diff --git a/Tests/helper.py b/Tests/helper.py
index d6a93a803..577e32d37 100644
--- a/Tests/helper.py
+++ b/Tests/helper.py
@@ -98,6 +98,7 @@ def assert_image_equal(a: Image.Image, b: Image.Image, msg: str | None = None) -
 def assert_image_equal_tofile(
     a: Image.Image, filename: str, msg: str | None = None, mode: str | None = None
 ) -> None:
+    img: Image.Image
     with Image.open(filename) as img:
         if mode:
             img = img.convert(mode)
@@ -142,6 +143,7 @@ def assert_image_similar_tofile(
     msg: str | None = None,
     mode: str | None = None,
 ) -> None:
+    img: Image.Image
     with Image.open(filename) as img:
         if mode:
             img = img.convert(mode)
diff --git a/Tests/test_bmp_reference.py b/Tests/test_bmp_reference.py
index 7f8487921..3c57ff8aa 100644
--- a/Tests/test_bmp_reference.py
+++ b/Tests/test_bmp_reference.py
@@ -92,8 +92,11 @@ def test_good() -> None:
 
     for f in get_files("g"):
         try:
+            im: Image.Image
             with Image.open(f) as im:
                 im.load()
+
+                compare: Image.Image
                 with Image.open(get_compare(f)) as compare:
                     compare.load()
                     if im.mode == "P":
diff --git a/Tests/test_file_apng.py b/Tests/test_file_apng.py
index e95850212..1e11554c8 100644
--- a/Tests/test_file_apng.py
+++ b/Tests/test_file_apng.py
@@ -12,6 +12,7 @@ from PIL import Image, ImageSequence, PngImagePlugin
 # (referenced from https://wiki.mozilla.org/APNG_Specification)
 def test_apng_basic() -> None:
     with Image.open("Tests/images/apng/single_frame.png") as im:
+        assert isinstance(im, PngImagePlugin.PngImageFile)
         assert not im.is_animated
         assert im.n_frames == 1
         assert im.get_format_mimetype() == "image/apng"
@@ -20,6 +21,7 @@ def test_apng_basic() -> None:
         assert im.getpixel((64, 32)) == (0, 255, 0, 255)
 
     with Image.open("Tests/images/apng/single_frame_default.png") as im:
+        assert isinstance(im, PngImagePlugin.PngImageFile)
         assert im.is_animated
         assert im.n_frames == 2
         assert im.get_format_mimetype() == "image/apng"
@@ -49,6 +51,7 @@ def test_apng_basic() -> None:
 )
 def test_apng_fdat(filename: str) -> None:
     with Image.open(filename) as im:
+        assert isinstance(im, PngImagePlugin.PngImageFile)
         im.seek(im.n_frames - 1)
         assert im.getpixel((0, 0)) == (0, 255, 0, 255)
         assert im.getpixel((64, 32)) == (0, 255, 0, 255)
@@ -56,31 +59,37 @@ def test_apng_fdat(filename: str) -> None:
 
 def test_apng_dispose() -> None:
     with Image.open("Tests/images/apng/dispose_op_none.png") as im:
+        assert isinstance(im, PngImagePlugin.PngImageFile)
         im.seek(im.n_frames - 1)
         assert im.getpixel((0, 0)) == (0, 255, 0, 255)
         assert im.getpixel((64, 32)) == (0, 255, 0, 255)
 
     with Image.open("Tests/images/apng/dispose_op_background.png") as im:
+        assert isinstance(im, PngImagePlugin.PngImageFile)
         im.seek(im.n_frames - 1)
         assert im.getpixel((0, 0)) == (0, 0, 0, 0)
         assert im.getpixel((64, 32)) == (0, 0, 0, 0)
 
     with Image.open("Tests/images/apng/dispose_op_background_final.png") as im:
+        assert isinstance(im, PngImagePlugin.PngImageFile)
         im.seek(im.n_frames - 1)
         assert im.getpixel((0, 0)) == (0, 255, 0, 255)
         assert im.getpixel((64, 32)) == (0, 255, 0, 255)
 
     with Image.open("Tests/images/apng/dispose_op_previous.png") as im:
+        assert isinstance(im, PngImagePlugin.PngImageFile)
         im.seek(im.n_frames - 1)
         assert im.getpixel((0, 0)) == (0, 255, 0, 255)
         assert im.getpixel((64, 32)) == (0, 255, 0, 255)
 
     with Image.open("Tests/images/apng/dispose_op_previous_final.png") as im:
+        assert isinstance(im, PngImagePlugin.PngImageFile)
         im.seek(im.n_frames - 1)
         assert im.getpixel((0, 0)) == (0, 255, 0, 255)
         assert im.getpixel((64, 32)) == (0, 255, 0, 255)
 
     with Image.open("Tests/images/apng/dispose_op_previous_first.png") as im:
+        assert isinstance(im, PngImagePlugin.PngImageFile)
         im.seek(im.n_frames - 1)
         assert im.getpixel((0, 0)) == (0, 0, 0, 0)
         assert im.getpixel((64, 32)) == (0, 0, 0, 0)
@@ -88,21 +97,25 @@ def test_apng_dispose() -> None:
 
 def test_apng_dispose_region() -> None:
     with Image.open("Tests/images/apng/dispose_op_none_region.png") as im:
+        assert isinstance(im, PngImagePlugin.PngImageFile)
         im.seek(im.n_frames - 1)
         assert im.getpixel((0, 0)) == (0, 255, 0, 255)
         assert im.getpixel((64, 32)) == (0, 255, 0, 255)
 
     with Image.open("Tests/images/apng/dispose_op_background_before_region.png") as im:
+        assert isinstance(im, PngImagePlugin.PngImageFile)
         im.seek(im.n_frames - 1)
         assert im.getpixel((0, 0)) == (0, 0, 0, 0)
         assert im.getpixel((64, 32)) == (0, 0, 0, 0)
 
     with Image.open("Tests/images/apng/dispose_op_background_region.png") as im:
+        assert isinstance(im, PngImagePlugin.PngImageFile)
         im.seek(im.n_frames - 1)
         assert im.getpixel((0, 0)) == (0, 0, 255, 255)
         assert im.getpixel((64, 32)) == (0, 0, 0, 0)
 
     with Image.open("Tests/images/apng/dispose_op_previous_region.png") as im:
+        assert isinstance(im, PngImagePlugin.PngImageFile)
         im.seek(im.n_frames - 1)
         assert im.getpixel((0, 0)) == (0, 255, 0, 255)
         assert im.getpixel((64, 32)) == (0, 255, 0, 255)
@@ -129,6 +142,7 @@ def test_apng_dispose_op_previous_frame() -> None:
     #     ],
     # )
     with Image.open("Tests/images/apng/dispose_op_previous_frame.png") as im:
+        assert isinstance(im, PngImagePlugin.PngImageFile)
         im.seek(im.n_frames - 1)
         assert im.getpixel((0, 0)) == (255, 0, 0, 255)
 
@@ -142,26 +156,31 @@ def test_apng_dispose_op_background_p_mode() -> None:
 
 def test_apng_blend() -> None:
     with Image.open("Tests/images/apng/blend_op_source_solid.png") as im:
+        assert isinstance(im, PngImagePlugin.PngImageFile)
         im.seek(im.n_frames - 1)
         assert im.getpixel((0, 0)) == (0, 255, 0, 255)
         assert im.getpixel((64, 32)) == (0, 255, 0, 255)
 
     with Image.open("Tests/images/apng/blend_op_source_transparent.png") as im:
+        assert isinstance(im, PngImagePlugin.PngImageFile)
         im.seek(im.n_frames - 1)
         assert im.getpixel((0, 0)) == (0, 0, 0, 0)
         assert im.getpixel((64, 32)) == (0, 0, 0, 0)
 
     with Image.open("Tests/images/apng/blend_op_source_near_transparent.png") as im:
+        assert isinstance(im, PngImagePlugin.PngImageFile)
         im.seek(im.n_frames - 1)
         assert im.getpixel((0, 0)) == (0, 255, 0, 2)
         assert im.getpixel((64, 32)) == (0, 255, 0, 2)
 
     with Image.open("Tests/images/apng/blend_op_over.png") as im:
+        assert isinstance(im, PngImagePlugin.PngImageFile)
         im.seek(im.n_frames - 1)
         assert im.getpixel((0, 0)) == (0, 255, 0, 255)
         assert im.getpixel((64, 32)) == (0, 255, 0, 255)
 
     with Image.open("Tests/images/apng/blend_op_over_near_transparent.png") as im:
+        assert isinstance(im, PngImagePlugin.PngImageFile)
         im.seek(im.n_frames - 1)
         assert im.getpixel((0, 0)) == (0, 255, 0, 97)
         assert im.getpixel((64, 32)) == (0, 255, 0, 255)
@@ -175,6 +194,7 @@ def test_apng_blend_transparency() -> None:
 
 def test_apng_chunk_order() -> None:
     with Image.open("Tests/images/apng/fctl_actl.png") as im:
+        assert isinstance(im, PngImagePlugin.PngImageFile)
         im.seek(im.n_frames - 1)
         assert im.getpixel((0, 0)) == (0, 255, 0, 255)
         assert im.getpixel((64, 32)) == (0, 255, 0, 255)
@@ -230,66 +250,78 @@ def test_apng_num_plays() -> None:
 
 def test_apng_mode() -> None:
     with Image.open("Tests/images/apng/mode_16bit.png") as im:
+        assert isinstance(im, PngImagePlugin.PngImageFile)
         assert im.mode == "RGBA"
         im.seek(im.n_frames - 1)
         assert im.getpixel((0, 0)) == (0, 0, 128, 191)
         assert im.getpixel((64, 32)) == (0, 0, 128, 191)
 
     with Image.open("Tests/images/apng/mode_grayscale.png") as im:
+        assert isinstance(im, PngImagePlugin.PngImageFile)
         assert im.mode == "L"
         im.seek(im.n_frames - 1)
         assert im.getpixel((0, 0)) == 128
         assert im.getpixel((64, 32)) == 255
 
     with Image.open("Tests/images/apng/mode_grayscale_alpha.png") as im:
+        assert isinstance(im, PngImagePlugin.PngImageFile)
         assert im.mode == "LA"
         im.seek(im.n_frames - 1)
         assert im.getpixel((0, 0)) == (128, 191)
         assert im.getpixel((64, 32)) == (128, 191)
 
     with Image.open("Tests/images/apng/mode_palette.png") as im:
+        assert isinstance(im, PngImagePlugin.PngImageFile)
         assert im.mode == "P"
         im.seek(im.n_frames - 1)
-        im = im.convert("RGB")
-        assert im.getpixel((0, 0)) == (0, 255, 0)
-        assert im.getpixel((64, 32)) == (0, 255, 0)
+        rgb_im = im.convert("RGB")
+        assert rgb_im.getpixel((0, 0)) == (0, 255, 0)
+        assert rgb_im.getpixel((64, 32)) == (0, 255, 0)
 
     with Image.open("Tests/images/apng/mode_palette_alpha.png") as im:
+        assert isinstance(im, PngImagePlugin.PngImageFile)
         assert im.mode == "P"
         im.seek(im.n_frames - 1)
-        im = im.convert("RGBA")
-        assert im.getpixel((0, 0)) == (255, 0, 0, 0)
-        assert im.getpixel((64, 32)) == (255, 0, 0, 0)
+        rgb_im = im.convert("RGBA")
+        assert rgb_im.getpixel((0, 0)) == (255, 0, 0, 0)
+        assert rgb_im.getpixel((64, 32)) == (255, 0, 0, 0)
 
     with Image.open("Tests/images/apng/mode_palette_1bit_alpha.png") as im:
+        assert isinstance(im, PngImagePlugin.PngImageFile)
         assert im.mode == "P"
         im.seek(im.n_frames - 1)
-        im = im.convert("RGBA")
-        assert im.getpixel((0, 0)) == (0, 0, 255, 128)
-        assert im.getpixel((64, 32)) == (0, 0, 255, 128)
+        rgb_im = im.convert("RGBA")
+        assert rgb_im.getpixel((0, 0)) == (0, 0, 255, 128)
+        assert rgb_im.getpixel((64, 32)) == (0, 0, 255, 128)
 
 
 def test_apng_chunk_errors() -> None:
     with Image.open("Tests/images/apng/chunk_no_actl.png") as im:
+        assert isinstance(im, PngImagePlugin.PngImageFile)
         assert not im.is_animated
 
     with pytest.warns(UserWarning):
         with Image.open("Tests/images/apng/chunk_multi_actl.png") as im:
             im.load()
+        assert isinstance(im, PngImagePlugin.PngImageFile)
         assert not im.is_animated
 
     with Image.open("Tests/images/apng/chunk_actl_after_idat.png") as im:
+        assert isinstance(im, PngImagePlugin.PngImageFile)
         assert not im.is_animated
 
     with Image.open("Tests/images/apng/chunk_no_fctl.png") as im:
+        assert isinstance(im, PngImagePlugin.PngImageFile)
         with pytest.raises(SyntaxError):
             im.seek(im.n_frames - 1)
 
     with Image.open("Tests/images/apng/chunk_repeat_fctl.png") as im:
+        assert isinstance(im, PngImagePlugin.PngImageFile)
         with pytest.raises(SyntaxError):
             im.seek(im.n_frames - 1)
 
     with Image.open("Tests/images/apng/chunk_no_fdat.png") as im:
+        assert isinstance(im, PngImagePlugin.PngImageFile)
         with pytest.raises(SyntaxError):
             im.seek(im.n_frames - 1)
 
@@ -297,18 +329,21 @@ def test_apng_chunk_errors() -> None:
 def test_apng_syntax_errors() -> None:
     with pytest.warns(UserWarning):
         with Image.open("Tests/images/apng/syntax_num_frames_zero.png") as im:
+            assert isinstance(im, PngImagePlugin.PngImageFile)
             assert not im.is_animated
             with pytest.raises(OSError):
                 im.load()
 
     with pytest.warns(UserWarning):
         with Image.open("Tests/images/apng/syntax_num_frames_zero_default.png") as im:
+            assert isinstance(im, PngImagePlugin.PngImageFile)
             assert not im.is_animated
             im.load()
 
     # we can handle this case gracefully
     exception = None
     with Image.open("Tests/images/apng/syntax_num_frames_low.png") as im:
+        assert isinstance(im, PngImagePlugin.PngImageFile)
         try:
             im.seek(im.n_frames - 1)
         except Exception as e:
@@ -317,11 +352,13 @@ def test_apng_syntax_errors() -> None:
 
     with pytest.raises(OSError):
         with Image.open("Tests/images/apng/syntax_num_frames_high.png") as im:
+            assert isinstance(im, PngImagePlugin.PngImageFile)
             im.seek(im.n_frames - 1)
             im.load()
 
     with pytest.warns(UserWarning):
         with Image.open("Tests/images/apng/syntax_num_frames_invalid.png") as im:
+            assert isinstance(im, PngImagePlugin.PngImageFile)
             assert not im.is_animated
             im.load()
 
@@ -341,6 +378,7 @@ def test_apng_syntax_errors() -> None:
 def test_apng_sequence_errors(test_file: str) -> None:
     with pytest.raises(SyntaxError):
         with Image.open(f"Tests/images/apng/{test_file}") as im:
+            assert isinstance(im, PngImagePlugin.PngImageFile)
             im.seek(im.n_frames - 1)
             im.load()
 
@@ -351,6 +389,8 @@ def test_apng_save(tmp_path: Path) -> None:
         im.save(test_file, save_all=True)
 
     with Image.open(test_file) as im:
+        assert isinstance(im, PngImagePlugin.PngImageFile)
+
         im.load()
         assert not im.is_animated
         assert im.n_frames == 1
@@ -366,6 +406,8 @@ def test_apng_save(tmp_path: Path) -> None:
         )
 
     with Image.open(test_file) as im:
+        assert isinstance(im, PngImagePlugin.PngImageFile)
+
         im.load()
         assert im.is_animated
         assert im.n_frames == 2
@@ -405,6 +447,8 @@ def test_apng_save_split_fdat(tmp_path: Path) -> None:
             append_images=frames,
         )
     with Image.open(test_file) as im:
+        assert isinstance(im, PngImagePlugin.PngImageFile)
+
         exception = None
         try:
             im.seek(im.n_frames - 1)
@@ -452,6 +496,7 @@ def test_apng_save_duration_loop(tmp_path: Path) -> None:
         test_file, save_all=True, append_images=[frame, frame], duration=[500, 100, 150]
     )
     with Image.open(test_file) as im:
+        assert isinstance(im, PngImagePlugin.PngImageFile)
         assert im.n_frames == 1
         assert "duration" not in im.info
 
@@ -463,6 +508,7 @@ def test_apng_save_duration_loop(tmp_path: Path) -> None:
         duration=[500, 100, 150],
     )
     with Image.open(test_file) as im:
+        assert isinstance(im, PngImagePlugin.PngImageFile)
         assert im.n_frames == 2
         assert im.info["duration"] == 600
 
@@ -473,6 +519,7 @@ def test_apng_save_duration_loop(tmp_path: Path) -> None:
     frame.info["duration"] = 300
     frame.save(test_file, save_all=True, append_images=[frame, different_frame])
     with Image.open(test_file) as im:
+        assert isinstance(im, PngImagePlugin.PngImageFile)
         assert im.n_frames == 2
         assert im.info["duration"] == 600
 
diff --git a/Tests/test_file_bmp.py b/Tests/test_file_bmp.py
index 2ff4160bd..4aafd5eb8 100644
--- a/Tests/test_file_bmp.py
+++ b/Tests/test_file_bmp.py
@@ -166,9 +166,9 @@ def test_save_dib(tmp_path: Path) -> None:
 def test_rgba_bitfields() -> None:
     # This test image has been manually hexedited
     # to change the bitfield compression in the header from XBGR to RGBA
-    with Image.open("Tests/images/rgb32bf-rgba.bmp") as im:
+    with Image.open("Tests/images/rgb32bf-rgba.bmp") as bmp_im:
         # So before the comparing the image, swap the channels
-        b, g, r = im.split()[1:]
+        b, g, r = bmp_im.split()[1:]
         im = Image.merge("RGB", (r, g, b))
 
     assert_image_equal_tofile(im, "Tests/images/bmp/q/rgb32bf-xbgr.bmp")
diff --git a/Tests/test_file_bufrstub.py b/Tests/test_file_bufrstub.py
index 77ee5b0ea..983eb381c 100644
--- a/Tests/test_file_bufrstub.py
+++ b/Tests/test_file_bufrstub.py
@@ -61,6 +61,7 @@ def test_handler(tmp_path: Path) -> None:
 
         def load(self, im: ImageFile.StubImageFile) -> Image.Image:
             self.loaded = True
+            assert im.fp is not None
             im.fp.close()
             return Image.new("RGB", (1, 1))
 
diff --git a/Tests/test_file_container.py b/Tests/test_file_container.py
index 237045acc..597ab5083 100644
--- a/Tests/test_file_container.py
+++ b/Tests/test_file_container.py
@@ -4,8 +4,6 @@ import pytest
 
 from PIL import ContainerIO, Image
 
-from .helper import hopper
-
 TEST_FILE = "Tests/images/dummy.container"
 
 
@@ -15,15 +13,15 @@ def test_sanity() -> None:
 
 
 def test_isatty() -> None:
-    with hopper() as im:
-        container = ContainerIO.ContainerIO(im, 0, 0)
+    with open(TEST_FILE, "rb") as fh:
+        container = ContainerIO.ContainerIO(fh, 0, 0)
 
     assert container.isatty() is False
 
 
 def test_seekable() -> None:
-    with hopper() as im:
-        container = ContainerIO.ContainerIO(im, 0, 0)
+    with open(TEST_FILE, "rb") as fh:
+        container = ContainerIO.ContainerIO(fh, 0, 0)
 
     assert container.seekable() is True
 
diff --git a/Tests/test_file_cur.py b/Tests/test_file_cur.py
index dbf1b866d..ff82e2983 100644
--- a/Tests/test_file_cur.py
+++ b/Tests/test_file_cur.py
@@ -26,6 +26,7 @@ def test_invalid_file() -> None:
     no_cursors_file = "Tests/images/no_cursors.cur"
 
     cur = CurImagePlugin.CurImageFile(TEST_FILE)
+    assert cur.fp is not None
     cur.fp.close()
     with open(no_cursors_file, "rb") as cur.fp:
         with pytest.raises(TypeError):
diff --git a/Tests/test_file_dcx.py b/Tests/test_file_dcx.py
index 65337cad9..0383bb746 100644
--- a/Tests/test_file_dcx.py
+++ b/Tests/test_file_dcx.py
@@ -65,12 +65,14 @@ def test_tell() -> None:
 
 def test_n_frames() -> None:
     with Image.open(TEST_FILE) as im:
+        assert isinstance(im, DcxImagePlugin.DcxImageFile)
         assert im.n_frames == 1
         assert not im.is_animated
 
 
 def test_eoferror() -> None:
     with Image.open(TEST_FILE) as im:
+        assert isinstance(im, DcxImagePlugin.DcxImageFile)
         n_frames = im.n_frames
 
         # Test seeking past the last frame
diff --git a/Tests/test_file_dds.py b/Tests/test_file_dds.py
index 9a826ebe8..d81b3f8f3 100644
--- a/Tests/test_file_dds.py
+++ b/Tests/test_file_dds.py
@@ -50,6 +50,7 @@ TEST_FILE_UNCOMPRESSED_RGB_WITH_ALPHA = "Tests/images/uncompressed_rgb.dds"
 )
 def test_sanity_dxt1_bc1(image_path: str) -> None:
     """Check DXT1 and BC1 images can be opened"""
+    target: Image.Image
     with Image.open(TEST_FILE_DXT1.replace(".dds", ".png")) as target:
         target = target.convert("RGBA")
     with Image.open(image_path) as im:
@@ -331,11 +332,13 @@ def test_dxt5_colorblock_alpha_issue_4142() -> None:
 
     with Image.open("Tests/images/dxt5-colorblock-alpha-issue-4142.dds") as im:
         px = im.getpixel((0, 0))
+        assert isinstance(px, tuple)
         assert px[0] != 0
         assert px[1] != 0
         assert px[2] != 0
 
         px = im.getpixel((1, 0))
+        assert isinstance(px, tuple)
         assert px[0] != 0
         assert px[1] != 0
         assert px[2] != 0
diff --git a/Tests/test_file_eps.py b/Tests/test_file_eps.py
index d54deb515..22519b813 100644
--- a/Tests/test_file_eps.py
+++ b/Tests/test_file_eps.py
@@ -85,6 +85,8 @@ simple_eps_file_with_long_binary_data = (
 def test_sanity(filename: str, size: tuple[int, int], scale: int) -> None:
     expected_size = tuple(s * scale for s in size)
     with Image.open(filename) as image:
+        assert isinstance(image, EpsImagePlugin.EpsImageFile)
+
         image.load(scale=scale)
         assert image.mode == "RGB"
         assert image.size == expected_size
@@ -94,10 +96,12 @@ def test_sanity(filename: str, size: tuple[int, int], scale: int) -> None:
 @pytest.mark.skipif(not HAS_GHOSTSCRIPT, reason="Ghostscript not available")
 def test_load() -> None:
     with Image.open(FILE1) as im:
-        assert im.load()[0, 0] == (255, 255, 255)
+        px = im.load()
+        assert px is not None
+        assert px[0, 0] == (255, 255, 255)
 
         # Test again now that it has already been loaded once
-        assert im.load()[0, 0] == (255, 255, 255)
+        assert px[0, 0] == (255, 255, 255)
 
 
 def test_binary() -> None:
@@ -215,6 +219,8 @@ def test_showpage() -> None:
 @pytest.mark.skipif(not HAS_GHOSTSCRIPT, reason="Ghostscript not available")
 def test_transparency() -> None:
     with Image.open("Tests/images/reqd_showpage.eps") as plot_image:
+        assert isinstance(plot_image, EpsImagePlugin.EpsImageFile)
+
         plot_image.load(transparency=True)
         assert plot_image.mode == "RGBA"
 
@@ -239,8 +245,8 @@ def test_bytesio_object() -> None:
     with Image.open(img_bytes) as img:
         img.load()
 
-        with Image.open(FILE1_COMPARE) as image1_scale1_compare:
-            image1_scale1_compare = image1_scale1_compare.convert("RGB")
+        with Image.open(FILE1_COMPARE) as im:
+            image1_scale1_compare = im.convert("RGB")
         image1_scale1_compare.load()
         assert_image_similar(img, image1_scale1_compare, 5)
 
@@ -265,16 +271,16 @@ def test_render_scale1() -> None:
     # Zero bounding box
     with Image.open(FILE1) as image1_scale1:
         image1_scale1.load()
-        with Image.open(FILE1_COMPARE) as image1_scale1_compare:
-            image1_scale1_compare = image1_scale1_compare.convert("RGB")
+        with Image.open(FILE1_COMPARE) as im:
+            image1_scale1_compare = im.convert("RGB")
         image1_scale1_compare.load()
         assert_image_similar(image1_scale1, image1_scale1_compare, 5)
 
     # Non-zero bounding box
     with Image.open(FILE2) as image2_scale1:
         image2_scale1.load()
-        with Image.open(FILE2_COMPARE) as image2_scale1_compare:
-            image2_scale1_compare = image2_scale1_compare.convert("RGB")
+        with Image.open(FILE2_COMPARE) as im:
+            image2_scale1_compare = im.convert("RGB")
         image2_scale1_compare.load()
         assert_image_similar(image2_scale1, image2_scale1_compare, 10)
 
@@ -286,17 +292,19 @@ def test_render_scale2() -> None:
 
     # Zero bounding box
     with Image.open(FILE1) as image1_scale2:
+        assert isinstance(image1_scale2, EpsImagePlugin.EpsImageFile)
         image1_scale2.load(scale=2)
-        with Image.open(FILE1_COMPARE_SCALE2) as image1_scale2_compare:
-            image1_scale2_compare = image1_scale2_compare.convert("RGB")
+        with Image.open(FILE1_COMPARE_SCALE2) as im:
+            image1_scale2_compare = im.convert("RGB")
         image1_scale2_compare.load()
         assert_image_similar(image1_scale2, image1_scale2_compare, 5)
 
     # Non-zero bounding box
     with Image.open(FILE2) as image2_scale2:
+        assert isinstance(image2_scale2, EpsImagePlugin.EpsImageFile)
         image2_scale2.load(scale=2)
-        with Image.open(FILE2_COMPARE_SCALE2) as image2_scale2_compare:
-            image2_scale2_compare = image2_scale2_compare.convert("RGB")
+        with Image.open(FILE2_COMPARE_SCALE2) as im:
+            image2_scale2_compare = im.convert("RGB")
         image2_scale2_compare.load()
         assert_image_similar(image2_scale2, image2_scale2_compare, 10)
 
@@ -304,9 +312,9 @@ def test_render_scale2() -> None:
 @pytest.mark.skipif(not HAS_GHOSTSCRIPT, reason="Ghostscript not available")
 @pytest.mark.parametrize("filename", (FILE1, FILE2, "Tests/images/illu10_preview.eps"))
 def test_resize(filename: str) -> None:
-    with Image.open(filename) as im:
+    with Image.open(filename) as img:
         new_size = (100, 100)
-        im = im.resize(new_size)
+        im = img.resize(new_size)
         assert im.size == new_size
 
 
diff --git a/Tests/test_file_fli.py b/Tests/test_file_fli.py
index f86fb8d09..d99b76f62 100644
--- a/Tests/test_file_fli.py
+++ b/Tests/test_file_fli.py
@@ -21,6 +21,8 @@ animated_test_file_with_prefix_chunk = "Tests/images/2422.flc"
 
 def test_sanity() -> None:
     with Image.open(static_test_file) as im:
+        assert isinstance(im, FliImagePlugin.FliImageFile)
+
         im.load()
         assert im.mode == "P"
         assert im.size == (128, 128)
@@ -28,6 +30,8 @@ def test_sanity() -> None:
         assert not im.is_animated
 
     with Image.open(animated_test_file) as im:
+        assert isinstance(im, FliImagePlugin.FliImageFile)
+
         assert im.mode == "P"
         assert im.size == (320, 200)
         assert im.format == "FLI"
@@ -39,6 +43,8 @@ def test_prefix_chunk() -> None:
     ImageFile.LOAD_TRUNCATED_IMAGES = True
     try:
         with Image.open(animated_test_file_with_prefix_chunk) as im:
+            assert isinstance(im, FliImagePlugin.FliImageFile)
+
             assert im.mode == "P"
             assert im.size == (320, 200)
             assert im.format == "FLI"
@@ -46,6 +52,7 @@ def test_prefix_chunk() -> None:
             assert im.is_animated
 
             palette = im.getpalette()
+            assert palette is not None
             assert palette[3:6] == [255, 255, 255]
             assert palette[381:384] == [204, 204, 12]
             assert palette[765:] == [252, 0, 0]
@@ -110,16 +117,19 @@ def test_palette_chunk_second() -> None:
 
 def test_n_frames() -> None:
     with Image.open(static_test_file) as im:
+        assert isinstance(im, FliImagePlugin.FliImageFile)
         assert im.n_frames == 1
         assert not im.is_animated
 
     with Image.open(animated_test_file) as im:
+        assert isinstance(im, FliImagePlugin.FliImageFile)
         assert im.n_frames == 384
         assert im.is_animated
 
 
 def test_eoferror() -> None:
     with Image.open(animated_test_file) as im:
+        assert isinstance(im, FliImagePlugin.FliImageFile)
         n_frames = im.n_frames
 
         # Test seeking past the last frame
diff --git a/Tests/test_file_fpx.py b/Tests/test_file_fpx.py
index e32f30a01..8d8064692 100644
--- a/Tests/test_file_fpx.py
+++ b/Tests/test_file_fpx.py
@@ -22,10 +22,11 @@ def test_sanity() -> None:
 
 def test_close() -> None:
     with Image.open("Tests/images/input_bw_one_band.fpx") as im:
-        pass
+        assert isinstance(im, FpxImagePlugin.FpxImageFile)
     assert im.ole.fp.closed
 
     im = Image.open("Tests/images/input_bw_one_band.fpx")
+    assert isinstance(im, FpxImagePlugin.FpxImageFile)
     im.close()
     assert im.ole.fp.closed
 
diff --git a/Tests/test_file_gbr.py b/Tests/test_file_gbr.py
index be98b08f2..19ef2ddde 100644
--- a/Tests/test_file_gbr.py
+++ b/Tests/test_file_gbr.py
@@ -14,10 +14,12 @@ def test_gbr_file() -> None:
 
 def test_load() -> None:
     with Image.open("Tests/images/gbr.gbr") as im:
-        assert im.load()[0, 0] == (0, 0, 0, 0)
+        px = im.load()
+        assert px is not None
+        assert px[0, 0] == (0, 0, 0, 0)
 
         # Test again now that it has already been loaded once
-        assert im.load()[0, 0] == (0, 0, 0, 0)
+        assert px[0, 0] == (0, 0, 0, 0)
 
 
 def test_multiple_load_operations() -> None:
diff --git a/Tests/test_file_gif.py b/Tests/test_file_gif.py
index 571fe1b9a..e8ec518a6 100644
--- a/Tests/test_file_gif.py
+++ b/Tests/test_file_gif.py
@@ -81,12 +81,16 @@ def test_invalid_file() -> None:
 def test_l_mode_transparency() -> None:
     with Image.open("Tests/images/no_palette_with_transparency.gif") as im:
         assert im.mode == "L"
-        assert im.load()[0, 0] == 128
+        px = im.load()
+        assert px is not None
+        assert px[0, 0] == 128
         assert im.info["transparency"] == 255
 
         im.seek(1)
         assert im.mode == "L"
-        assert im.load()[0, 0] == 128
+        px = im.load()
+        assert px is not None
+        assert px[0, 0] == 128
 
 
 def test_l_mode_after_rgb() -> None:
@@ -221,6 +225,7 @@ def test_optimize_if_palette_can_be_reduced_by_half() -> None:
         out = BytesIO()
         im.save(out, "GIF", optimize=optimize)
         with Image.open(out) as reloaded:
+            assert reloaded.palette is not None
             assert len(reloaded.palette.palette) // 3 == colors
 
 
@@ -277,6 +282,7 @@ def test_roundtrip_save_all(tmp_path: Path) -> None:
         im.save(out, save_all=True)
 
     with Image.open(out) as reread:
+        assert isinstance(reread, GifImagePlugin.GifImageFile)
         assert reread.n_frames == 5
 
 
@@ -302,10 +308,14 @@ def test_roundtrip_save_all_1(tmp_path: Path) -> None:
     ),
 )
 def test_loading_multiple_palettes(path: str, mode: str) -> None:
+    im: Image.Image
     with Image.open(path) as im:
         assert im.mode == "P"
+        assert im.palette is not None
         first_frame_colors = im.palette.colors.keys()
-        original_color = im.convert("RGB").load()[0, 0]
+        px = im.convert("RGB").load()
+        assert px is not None
+        original_color = px[0, 0]
 
         im.seek(1)
         assert im.mode == mode
@@ -313,10 +323,14 @@ def test_loading_multiple_palettes(path: str, mode: str) -> None:
             im = im.convert("RGB")
 
         # Check a color only from the old palette
-        assert im.load()[0, 0] == original_color
+        px = im.load()
+        assert px is not None
+        assert px[0, 0] == original_color
 
         # Check a color from the new palette
-        assert im.load()[24, 24] not in first_frame_colors
+        px = im.load()
+        assert px is not None
+        assert px[24, 24] not in first_frame_colors
 
 
 def test_headers_saving_for_animated_gifs(tmp_path: Path) -> None:
@@ -334,7 +348,7 @@ def test_headers_saving_for_animated_gifs(tmp_path: Path) -> None:
 
 def test_palette_handling(tmp_path: Path) -> None:
     # see https://github.com/python-pillow/Pillow/issues/513
-
+    im: Image.Image
     with Image.open(TEST_GIF) as im:
         im = im.convert("RGB")
 
@@ -358,8 +372,8 @@ def test_palette_434(tmp_path: Path) -> None:
 
         return reloaded
 
-    orig = "Tests/images/test.colors.gif"
-    with Image.open(orig) as im:
+    im: Image.Image
+    with Image.open("Tests/images/test.colors.gif") as im:
         with roundtrip(im) as reloaded:
             assert_image_similar(im, reloaded, 1)
         with roundtrip(im, optimize=True) as reloaded:
@@ -374,6 +388,7 @@ def test_palette_434(tmp_path: Path) -> None:
 
 @pytest.mark.skipif(not netpbm_available(), reason="Netpbm not available")
 def test_save_netpbm_bmp_mode(tmp_path: Path) -> None:
+    img: Image.Image
     with Image.open(TEST_GIF) as img:
         img = img.convert("RGB")
 
@@ -386,6 +401,7 @@ def test_save_netpbm_bmp_mode(tmp_path: Path) -> None:
 
 @pytest.mark.skipif(not netpbm_available(), reason="Netpbm not available")
 def test_save_netpbm_l_mode(tmp_path: Path) -> None:
+    img: Image.Image
     with Image.open(TEST_GIF) as img:
         img = img.convert("L")
 
@@ -438,10 +454,12 @@ def test_seek_rewind() -> None:
 def test_n_frames(path: str, n_frames: int) -> None:
     # Test is_animated before n_frames
     with Image.open(path) as im:
+        assert isinstance(im, GifImagePlugin.GifImageFile)
         assert im.is_animated == (n_frames != 1)
 
     # Test is_animated after n_frames
     with Image.open(path) as im:
+        assert isinstance(im, GifImagePlugin.GifImageFile)
         assert im.n_frames == n_frames
         assert im.is_animated == (n_frames != 1)
 
@@ -451,6 +469,7 @@ def test_no_change() -> None:
     with Image.open("Tests/images/dispose_bgnd.gif") as im:
         im.seek(1)
         expected = im.copy()
+        assert isinstance(im, GifImagePlugin.GifImageFile)
         assert im.n_frames == 5
         assert_image_equal(im, expected)
 
@@ -458,17 +477,20 @@ def test_no_change() -> None:
     with Image.open("Tests/images/dispose_bgnd.gif") as im:
         im.seek(3)
         expected = im.copy()
+        assert isinstance(im, GifImagePlugin.GifImageFile)
         assert im.is_animated
         assert_image_equal(im, expected)
 
     with Image.open("Tests/images/comment_after_only_frame.gif") as im:
         expected = Image.new("P", (1, 1))
+        assert isinstance(im, GifImagePlugin.GifImageFile)
         assert not im.is_animated
         assert_image_equal(im, expected)
 
 
 def test_eoferror() -> None:
     with Image.open(TEST_GIF) as im:
+        assert isinstance(im, GifImagePlugin.GifImageFile)
         n_frames = im.n_frames
 
         # Test seeking past the last frame
@@ -483,11 +505,13 @@ def test_eoferror() -> None:
 def test_first_frame_transparency() -> None:
     with Image.open("Tests/images/first_frame_transparency.gif") as im:
         px = im.load()
+        assert px is not None
         assert px[0, 0] == im.info["transparency"]
 
 
 def test_dispose_none() -> None:
     with Image.open("Tests/images/dispose_none.gif") as img:
+        assert isinstance(img, GifImagePlugin.GifImageFile)
         try:
             while True:
                 img.seek(img.tell() + 1)
@@ -511,6 +535,7 @@ def test_dispose_none_load_end() -> None:
 
 def test_dispose_background() -> None:
     with Image.open("Tests/images/dispose_bgnd.gif") as img:
+        assert isinstance(img, GifImagePlugin.GifImageFile)
         try:
             while True:
                 img.seek(img.tell() + 1)
@@ -523,7 +548,10 @@ def test_dispose_background_transparency() -> None:
     with Image.open("Tests/images/dispose_bgnd_transparency.gif") as img:
         img.seek(2)
         px = img.load()
-        assert px[35, 30][3] == 0
+        assert px is not None
+        value = px[35, 30]
+        assert isinstance(value, tuple)
+        assert value[3] == 0
 
 
 @pytest.mark.parametrize(
@@ -565,6 +593,7 @@ def test_transparent_dispose(
 
 def test_dispose_previous() -> None:
     with Image.open("Tests/images/dispose_prev.gif") as img:
+        assert isinstance(img, GifImagePlugin.GifImageFile)
         try:
             while True:
                 img.seek(img.tell() + 1)
@@ -602,6 +631,7 @@ def test_save_dispose(tmp_path: Path) -> None:
     for method in range(0, 4):
         im_list[0].save(out, save_all=True, append_images=im_list[1:], disposal=method)
         with Image.open(out) as img:
+            assert isinstance(img, GifImagePlugin.GifImageFile)
             for _ in range(2):
                 img.seek(img.tell() + 1)
                 assert img.disposal_method == method
@@ -615,6 +645,7 @@ def test_save_dispose(tmp_path: Path) -> None:
     )
 
     with Image.open(out) as img:
+        assert isinstance(img, GifImagePlugin.GifImageFile)
         for i in range(2):
             img.seek(img.tell() + 1)
             assert img.disposal_method == i + 1
@@ -737,6 +768,7 @@ def test_dispose2_background_frame(tmp_path: Path) -> None:
     im_list[0].save(out, save_all=True, append_images=im_list[1:], disposal=2)
 
     with Image.open(out) as im:
+        assert isinstance(im, GifImagePlugin.GifImageFile)
         assert im.n_frames == 3
 
 
@@ -903,6 +935,8 @@ def test_identical_frames(tmp_path: Path) -> None:
         out, save_all=True, append_images=im_list[1:], duration=duration_list
     )
     with Image.open(out) as reread:
+        assert isinstance(reread, GifImagePlugin.GifImageFile)
+
         # Assert that the first three frames were combined
         assert reread.n_frames == 2
 
@@ -932,6 +966,8 @@ def test_identical_frames_to_single_frame(
 
     im_list[0].save(out, save_all=True, append_images=im_list[1:], duration=duration)
     with Image.open(out) as reread:
+        assert isinstance(reread, GifImagePlugin.GifImageFile)
+
         # Assert that all frames were combined
         assert reread.n_frames == 1
 
@@ -979,9 +1015,9 @@ def test_webp_background(tmp_path: Path) -> None:
 
     # Test opaque WebP background
     if features.check("webp"):
-        with Image.open("Tests/images/hopper.webp") as im:
-            assert im.info["background"] == (255, 255, 255, 255)
-            im.save(out)
+        with Image.open("Tests/images/hopper.webp") as img:
+            assert img.info["background"] == (255, 255, 255, 255)
+            img.save(out)
 
     # Test non-opaque WebP background
     im = Image.new("L", (100, 100), "#000")
@@ -990,6 +1026,7 @@ def test_webp_background(tmp_path: Path) -> None:
 
 
 def test_comment(tmp_path: Path) -> None:
+    im: Image.Image
     with Image.open(TEST_GIF) as im:
         assert im.info["comment"] == b"File written by Adobe Photoshop\xa8 4.0"
 
@@ -1118,6 +1155,7 @@ def test_append_images(tmp_path: Path) -> None:
     im.copy().save(out, save_all=True, append_images=ims)
 
     with Image.open(out) as reread:
+        assert isinstance(reread, GifImagePlugin.GifImageFile)
         assert reread.n_frames == 3
 
     # Tests appending using a generator
@@ -1127,6 +1165,7 @@ def test_append_images(tmp_path: Path) -> None:
     im.save(out, save_all=True, append_images=im_generator(ims))
 
     with Image.open(out) as reread:
+        assert isinstance(reread, GifImagePlugin.GifImageFile)
         assert reread.n_frames == 3
 
     # Tests appending single and multiple frame images
@@ -1135,6 +1174,7 @@ def test_append_images(tmp_path: Path) -> None:
             im.save(out, save_all=True, append_images=[im2])
 
     with Image.open(out) as reread:
+        assert isinstance(reread, GifImagePlugin.GifImageFile)
         assert reread.n_frames == 10
 
 
@@ -1235,6 +1275,7 @@ def test_bbox(tmp_path: Path) -> None:
     im.save(out, save_all=True, append_images=ims)
 
     with Image.open(out) as reread:
+        assert isinstance(reread, GifImagePlugin.GifImageFile)
         assert reread.n_frames == 2
 
 
@@ -1247,6 +1288,7 @@ def test_bbox_alpha(tmp_path: Path) -> None:
     im.save(out, save_all=True, append_images=[im2])
 
     with Image.open(out) as reread:
+        assert isinstance(reread, GifImagePlugin.GifImageFile)
         assert reread.n_frames == 2
 
 
@@ -1308,6 +1350,9 @@ def test_palette_save_all_P(tmp_path: Path) -> None:
     with Image.open(out) as im:
         # Assert that the frames are correct, and each frame has the same palette
         assert_image_equal(im.convert("RGB"), frames[0].convert("RGB"))
+        assert isinstance(im, GifImagePlugin.GifImageFile)
+        assert im.palette is not None
+        assert im.global_palette is not None
         assert im.palette.palette == im.global_palette.palette
 
         im.seek(1)
@@ -1373,7 +1418,9 @@ def test_getdata() -> None:
 def test_lzw_bits() -> None:
     # see https://github.com/python-pillow/Pillow/issues/2811
     with Image.open("Tests/images/issue_2811.gif") as im:
-        assert im.tile[0][3][0] == 11  # LZW bits
+        args = im.tile[0][3]
+        assert isinstance(args, tuple)
+        assert args[0] == 11  # LZW bits
         # codec error prepatch
         im.load()
 
@@ -1398,6 +1445,7 @@ def test_extents(
     GifImagePlugin.LOADING_STRATEGY = loading_strategy
     try:
         with Image.open("Tests/images/" + test_file) as im:
+            assert isinstance(im, GifImagePlugin.GifImageFile)
             assert im.size == (100, 100)
 
             # Check that n_frames does not change the size
@@ -1428,4 +1476,8 @@ def test_saving_rgba(tmp_path: Path) -> None:
 
     with Image.open(out) as reloaded:
         reloaded_rgba = reloaded.convert("RGBA")
-        assert reloaded_rgba.load()[0, 0][3] == 0
+        px = reloaded_rgba.load()
+        assert px is not None
+        value = px[0, 0]
+        assert isinstance(value, tuple)
+        assert value[3] == 0
diff --git a/Tests/test_file_gribstub.py b/Tests/test_file_gribstub.py
index aba473d24..65b1c506e 100644
--- a/Tests/test_file_gribstub.py
+++ b/Tests/test_file_gribstub.py
@@ -59,8 +59,9 @@ def test_handler(tmp_path: Path) -> None:
         def open(self, im: Image.Image) -> None:
             self.opened = True
 
-        def load(self, im: Image.Image) -> Image.Image:
+        def load(self, im: ImageFile.ImageFile) -> Image.Image:
             self.loaded = True
+            assert im.fp is not None
             im.fp.close()
             return Image.new("RGB", (1, 1))
 
diff --git a/Tests/test_file_hdf5stub.py b/Tests/test_file_hdf5stub.py
index 8275bd0d8..b8a8ecce6 100644
--- a/Tests/test_file_hdf5stub.py
+++ b/Tests/test_file_hdf5stub.py
@@ -61,8 +61,9 @@ def test_handler(tmp_path: Path) -> None:
         def open(self, im: Image.Image) -> None:
             self.opened = True
 
-        def load(self, im: Image.Image) -> Image.Image:
+        def load(self, im: ImageFile.ImageFile) -> Image.Image:
             self.loaded = True
+            assert im.fp is not None
             im.fp.close()
             return Image.new("RGB", (1, 1))
 
diff --git a/Tests/test_file_icns.py b/Tests/test_file_icns.py
index 488984aef..91fd81409 100644
--- a/Tests/test_file_icns.py
+++ b/Tests/test_file_icns.py
@@ -30,10 +30,14 @@ def test_sanity() -> None:
 
 def test_load() -> None:
     with Image.open(TEST_FILE) as im:
-        assert im.load()[0, 0] == (0, 0, 0, 0)
+        px = im.load()
+        assert px is not None
+        assert px[0, 0] == (0, 0, 0, 0)
 
         # Test again now that it has already been loaded once
-        assert im.load()[0, 0] == (0, 0, 0, 0)
+        px = im.load()
+        assert px is not None
+        assert px[0, 0] == (0, 0, 0, 0)
 
 
 def test_save(tmp_path: Path) -> None:
@@ -63,6 +67,7 @@ def test_save_append_images(tmp_path: Path) -> None:
         assert_image_similar_tofile(im, temp_file, 1)
 
         with Image.open(temp_file) as reread:
+            assert isinstance(reread, IcnsImagePlugin.IcnsImageFile)
             reread.size = (16, 16, 2)
             reread.load()
             assert_image_equal(reread, provided_im)
@@ -84,6 +89,7 @@ def test_sizes() -> None:
     # Check that we can load all of the sizes, and that the final pixel
     # dimensions are as expected
     with Image.open(TEST_FILE) as im:
+        assert isinstance(im, IcnsImagePlugin.IcnsImageFile)
         for w, h, r in im.info["sizes"]:
             wr = w * r
             hr = h * r
@@ -105,6 +111,7 @@ def test_older_icon() -> None:
             wr = w * r
             hr = h * r
             with Image.open("Tests/images/pillow2.icns") as im2:
+                assert isinstance(im2, IcnsImagePlugin.IcnsImageFile)
                 im2.size = (w, h, r)
                 im2.load()
                 assert im2.mode == "RGBA"
@@ -122,6 +129,7 @@ def test_jp2_icon() -> None:
             wr = w * r
             hr = h * r
             with Image.open("Tests/images/pillow3.icns") as im2:
+                assert isinstance(im2, IcnsImagePlugin.IcnsImageFile)
                 im2.size = (w, h, r)
                 im2.load()
                 assert im2.mode == "RGBA"
diff --git a/Tests/test_file_ico.py b/Tests/test_file_ico.py
index 37770498a..c86ade12d 100644
--- a/Tests/test_file_ico.py
+++ b/Tests/test_file_ico.py
@@ -24,7 +24,9 @@ def test_sanity() -> None:
 
 def test_load() -> None:
     with Image.open(TEST_ICO_FILE) as im:
-        assert im.load()[0, 0] == (1, 1, 9, 255)
+        px = im.load()
+        assert px is not None
+        assert px[0, 0] == (1, 1, 9, 255)
 
 
 def test_mask() -> None:
@@ -75,6 +77,7 @@ def test_save_to_bytes() -> None:
     # The other one
     output.seek(0)
     with Image.open(output) as reloaded:
+        assert isinstance(reloaded, IcoImagePlugin.IcoImageFile)
         reloaded.size = (32, 32)
 
         assert im.mode == reloaded.mode
@@ -92,6 +95,7 @@ def test_getpixel(tmp_path: Path) -> None:
     im.save(temp_file, "ico", sizes=[(32, 32), (64, 64)])
 
     with Image.open(temp_file) as reloaded:
+        assert isinstance(reloaded, IcoImagePlugin.IcoImageFile)
         reloaded.load()
         reloaded.size = (32, 32)
 
@@ -165,6 +169,7 @@ def test_save_to_bytes_bmp(mode: str) -> None:
     # The other one
     output.seek(0)
     with Image.open(output) as reloaded:
+        assert isinstance(reloaded, IcoImagePlugin.IcoImageFile)
         reloaded.size = (32, 32)
 
         assert "RGBA" == reloaded.mode
@@ -176,6 +181,7 @@ def test_save_to_bytes_bmp(mode: str) -> None:
 
 def test_incorrect_size() -> None:
     with Image.open(TEST_ICO_FILE) as im:
+        assert isinstance(im, IcoImagePlugin.IcoImageFile)
         with pytest.raises(ValueError):
             im.size = (1, 1)
 
@@ -217,6 +223,7 @@ def test_save_append_images(tmp_path: Path) -> None:
     im.save(outfile, sizes=[(32, 32), (128, 128)], append_images=[provided_im])
 
     with Image.open(outfile) as reread:
+        assert isinstance(reread, IcoImagePlugin.IcoImageFile)
         assert_image_equal(reread, hopper("RGBA"))
 
         reread.size = (32, 32)
@@ -253,8 +260,7 @@ def test_truncated_mask() -> None:
 
     try:
         with Image.open(io.BytesIO(data)) as im:
-            with Image.open("Tests/images/hopper_mask.png") as expected:
-                assert im.mode == "1"
+            assert im.mode == "1"
 
         # 32 bpp
         output = io.BytesIO()
diff --git a/Tests/test_file_im.py b/Tests/test_file_im.py
index 036965bf5..787a36b26 100644
--- a/Tests/test_file_im.py
+++ b/Tests/test_file_im.py
@@ -64,12 +64,14 @@ def test_tell() -> None:
 
 def test_n_frames() -> None:
     with Image.open(TEST_IM) as im:
+        assert isinstance(im, ImImagePlugin.ImImageFile)
         assert im.n_frames == 1
         assert not im.is_animated
 
 
 def test_eoferror() -> None:
     with Image.open(TEST_IM) as im:
+        assert isinstance(im, ImImagePlugin.ImImageFile)
         n_frames = im.n_frames
 
         # Test seeking past the last frame
diff --git a/Tests/test_file_jpeg.py b/Tests/test_file_jpeg.py
index cde951395..d3164c235 100644
--- a/Tests/test_file_jpeg.py
+++ b/Tests/test_file_jpeg.py
@@ -91,6 +91,7 @@ class TestFileJpeg:
     def test_app(self) -> None:
         # Test APP/COM reader (@PIL135)
         with Image.open(TEST_FILE) as im:
+            assert isinstance(im, JpegImagePlugin.JpegImageFile)
             assert im.applist[0] == ("APP0", b"JFIF\x00\x01\x01\x01\x00`\x00`\x00\x00")
             assert im.applist[1] == (
                 "COM",
@@ -131,26 +132,30 @@ class TestFileJpeg:
         f = "Tests/images/pil_sample_cmyk.jpg"
         with Image.open(f) as im:
             # the source image has red pixels in the upper left corner.
-            c, m, y, k = (x / 255.0 for x in im.getpixel((0, 0)))
+            value = im.getpixel((0, 0))
+            assert isinstance(value, tuple)
+            c, m, y, k = (x / 255.0 for x in value)
             assert c == 0.0
             assert m > 0.8
             assert y > 0.8
             assert k == 0.0
             # the opposite corner is black
-            c, m, y, k = (
-                x / 255.0 for x in im.getpixel((im.size[0] - 1, im.size[1] - 1))
-            )
+            value = im.getpixel((im.size[0] - 1, im.size[1] - 1))
+            assert isinstance(value, tuple)
+            c, m, y, k = (x / 255.0 for x in value)
             assert k > 0.9
             # roundtrip, and check again
             im = self.roundtrip(im)
-            c, m, y, k = (x / 255.0 for x in im.getpixel((0, 0)))
+            value = im.getpixel((0, 0))
+            assert isinstance(value, tuple)
+            c, m, y, k = (x / 255.0 for x in value)
             assert c == 0.0
             assert m > 0.8
             assert y > 0.8
             assert k == 0.0
-            c, m, y, k = (
-                x / 255.0 for x in im.getpixel((im.size[0] - 1, im.size[1] - 1))
-            )
+            value = im.getpixel((im.size[0] - 1, im.size[1] - 1))
+            assert isinstance(value, tuple)
+            c, m, y, k = (x / 255.0 for x in value)
             assert k > 0.9
 
     def test_rgb(self) -> None:
@@ -309,6 +314,8 @@ class TestFileJpeg:
 
     def test_exif_typeerror(self) -> None:
         with Image.open("Tests/images/exif_typeerror.jpg") as im:
+            assert isinstance(im, JpegImagePlugin.JpegImageFile)
+
             # Should not raise a TypeError
             im._getexif()
 
@@ -324,8 +331,10 @@ class TestFileJpeg:
 
         # Reading
         with Image.open("Tests/images/exif_gps.jpg") as im:
-            exif = im._getexif()
-            assert exif[gps_index] == expected_exif_gps
+            assert isinstance(im, JpegImagePlugin.JpegImageFile)
+            exif_data = im._getexif()
+            assert exif_data is not None
+            assert exif_data[gps_index] == expected_exif_gps
 
         # Writing
         f = str(tmp_path / "temp.jpg")
@@ -334,8 +343,10 @@ class TestFileJpeg:
         hopper().save(f, exif=exif)
 
         with Image.open(f) as reloaded:
-            exif = reloaded._getexif()
-            assert exif[gps_index] == expected_exif_gps
+            assert isinstance(reloaded, JpegImagePlugin.JpegImageFile)
+            exif_data = reloaded._getexif()
+            assert exif_data is not None
+            assert exif_data[gps_index] == expected_exif_gps
 
     def test_empty_exif_gps(self) -> None:
         with Image.open("Tests/images/empty_gps_ifd.jpg") as im:
@@ -363,6 +374,7 @@ class TestFileJpeg:
         exifs = []
         for i in range(2):
             with Image.open("Tests/images/exif-200dpcm.jpg") as im:
+                assert isinstance(im, JpegImagePlugin.JpegImageFile)
                 exifs.append(im._getexif())
         assert exifs[0] == exifs[1]
 
@@ -396,13 +408,18 @@ class TestFileJpeg:
         }
 
         with Image.open("Tests/images/exif_gps.jpg") as im:
+            assert isinstance(im, JpegImagePlugin.JpegImageFile)
+
             exif = im._getexif()
+            assert exif is not None
 
         for tag, value in expected_exif.items():
             assert value == exif[tag]
 
     def test_exif_gps_typeerror(self) -> None:
         with Image.open("Tests/images/exif_gps_typeerror.jpg") as im:
+            assert isinstance(im, JpegImagePlugin.JpegImageFile)
+
             # Should not raise a TypeError
             im._getexif()
 
@@ -478,7 +495,9 @@ class TestFileJpeg:
 
     def test_exif(self) -> None:
         with Image.open("Tests/images/pil_sample_rgb.jpg") as im:
+            assert isinstance(im, JpegImagePlugin.JpegImageFile)
             info = im._getexif()
+            assert info is not None
             assert info[305] == "Adobe Photoshop CS Macintosh"
 
     def test_get_child_images(self) -> None:
@@ -490,6 +509,7 @@ class TestFileJpeg:
 
     def test_mp(self) -> None:
         with Image.open("Tests/images/pil_sample_rgb.jpg") as im:
+            assert isinstance(im, JpegImagePlugin.JpegImageFile)
             assert im._getmp() is None
 
     def test_quality_keep(self, tmp_path: Path) -> None:
@@ -547,12 +567,14 @@ class TestFileJpeg:
                 f = str(tmp_path / "temp.jpg")
                 im.save(f, qtables=[[n] * 64] * n)
             with Image.open(f) as im:
+                assert isinstance(im, JpegImagePlugin.JpegImageFile)
                 assert len(im.quantization) == n
                 reloaded = self.roundtrip(im, qtables="keep")
                 assert im.quantization == reloaded.quantization
                 assert max(reloaded.quantization[0]) <= 255
 
         with Image.open("Tests/images/hopper.jpg") as im:
+            assert isinstance(im, JpegImagePlugin.JpegImageFile)
             qtables = im.quantization
             reloaded = self.roundtrip(im, qtables=qtables, subsampling=0)
             assert im.quantization == reloaded.quantization
@@ -652,6 +674,7 @@ class TestFileJpeg:
 
     def test_load_16bit_qtables(self) -> None:
         with Image.open("Tests/images/hopper_16bit_qtables.jpg") as im:
+            assert isinstance(im, JpegImagePlugin.JpegImageFile)
             assert len(im.quantization) == 2
             assert len(im.quantization[0]) == 64
             assert max(im.quantization[0]) > 255
@@ -659,10 +682,12 @@ class TestFileJpeg:
     def test_save_multiple_16bit_qtables(self) -> None:
         with Image.open("Tests/images/hopper_16bit_qtables.jpg") as im:
             im2 = self.roundtrip(im, qtables="keep")
+            assert isinstance(im, JpegImagePlugin.JpegImageFile)
             assert im.quantization == im2.quantization
 
     def test_save_single_16bit_qtable(self) -> None:
         with Image.open("Tests/images/hopper_16bit_qtables.jpg") as im:
+            assert isinstance(im, JpegImagePlugin.JpegImageFile)
             im2 = self.roundtrip(im, qtables={0: im.quantization[0]})
             assert len(im2.quantization) == 1
             assert im2.quantization[0] == im.quantization[0]
@@ -693,9 +718,10 @@ class TestFileJpeg:
 
     @pytest.mark.skipif(not djpeg_available(), reason="djpeg not available")
     def test_load_djpeg(self) -> None:
-        with Image.open(TEST_FILE) as img:
-            img.load_djpeg()
-            assert_image_similar_tofile(img, TEST_FILE, 5)
+        with Image.open(TEST_FILE) as im:
+            assert isinstance(im, JpegImagePlugin.JpegImageFile)
+            im.load_djpeg()
+            assert_image_similar_tofile(im, TEST_FILE, 5)
 
     @pytest.mark.skipif(not cjpeg_available(), reason="cjpeg not available")
     def test_save_cjpeg(self, tmp_path: Path) -> None:
@@ -868,7 +894,10 @@ class TestFileJpeg:
         # in contrast to normal 8
         with Image.open("Tests/images/exif-ifd-offset.jpg") as im:
             # Act / Assert
-            assert im._getexif()[306] == "2017:03:13 23:03:09"
+            assert isinstance(im, JpegImagePlugin.JpegImageFile)
+            exif = im._getexif()
+            assert exif is not None
+            assert exif[306] == "2017:03:13 23:03:09"
 
     def test_multiple_exif(self) -> None:
         with Image.open("Tests/images/multiple_exif.jpg") as im:
@@ -896,6 +925,7 @@ class TestFileJpeg:
 
     def test_photoshop_malformed_and_multiple(self) -> None:
         with Image.open("Tests/images/app13-multiple.jpg") as im:
+            assert isinstance(im, JpegImagePlugin.JpegImageFile)
             assert "photoshop" in im.info
             assert 24 == len(im.info["photoshop"])
             apps_13_lengths = [len(v) for k, v in im.applist if k == "APP13"]
@@ -1020,7 +1050,7 @@ class TestFileJpeg:
 
         with Image.open(TEST_FILE) as im:
             im.tile = [
-                ("INFINITE", (0, 0, 128, 128), 0, ("RGB", 0, 1)),
+                ImageFile._Tile("INFINITE", (0, 0, 128, 128), 0, ("RGB", 0, 1)),
             ]
             ImageFile.LOAD_TRUNCATED_IMAGES = True
             im.load()
@@ -1067,6 +1097,7 @@ class TestFileJpeg:
 
     def test_deprecation(self) -> None:
         with Image.open(TEST_FILE) as im:
+            assert isinstance(im, JpegImagePlugin.JpegImageFile)
             with pytest.warns(DeprecationWarning):
                 assert im.huffman_ac == {}
             with pytest.warns(DeprecationWarning):
@@ -1083,8 +1114,9 @@ class TestFileCloseW32:
             im.save(tmpfile)
 
         im = Image.open(tmpfile)
+        assert im.fp is not None
+        assert not im.fp.closed
         fp = im.fp
-        assert not fp.closed
         with pytest.raises(OSError):
             os.remove(tmpfile)
         im.load()
diff --git a/Tests/test_file_jpeg2k.py b/Tests/test_file_jpeg2k.py
index 26b085601..5976a9851 100644
--- a/Tests/test_file_jpeg2k.py
+++ b/Tests/test_file_jpeg2k.py
@@ -54,6 +54,7 @@ def test_sanity() -> None:
 
     with Image.open("Tests/images/test-card-lossless.jp2") as im:
         px = im.load()
+        assert px is not None
         assert px[0, 0] == (0, 0, 0)
         assert im.mode == "RGB"
         assert im.size == (640, 480)
@@ -154,7 +155,7 @@ def test_reduce() -> None:
     with Image.open("Tests/images/test-card-lossless.jp2") as im:
         assert callable(im.reduce)
 
-        im.reduce = 2
+        im.reduce = 2  # type: ignore[method-assign, assignment]
         assert im.reduce == 2
 
         im.load()
@@ -221,12 +222,14 @@ def test_layers() -> None:
     out.seek(0)
 
     with Image.open(out) as im:
+        assert isinstance(im, Jpeg2KImagePlugin.Jpeg2KImageFile)
         im.layers = 1
         im.load()
         assert_image_similar(im, test_card, 13)
 
     out.seek(0)
     with Image.open(out) as im:
+        assert isinstance(im, Jpeg2KImagePlugin.Jpeg2KImageFile)
         im.layers = 3
         im.load()
         assert_image_similar(im, test_card, 0.4)
@@ -397,6 +400,7 @@ def test_subsampling_decode(name: str) -> None:
 def test_pclr() -> None:
     with Image.open(f"{EXTRA_DIR}/issue104_jpxstream.jp2") as im:
         assert im.mode == "P"
+        assert im.palette is not None
         assert len(im.palette.colors) == 256
         assert im.palette.colors[(255, 255, 255)] == 0
 
@@ -404,6 +408,7 @@ def test_pclr() -> None:
         f"{EXTRA_DIR}/147af3f1083de4393666b7d99b01b58b_signal_sigsegv_130c531_6155_5136.jp2"
     ) as im:
         assert im.mode == "P"
+        assert im.palette is not None
         assert len(im.palette.colors) == 139
         assert im.palette.colors[(0, 0, 0, 0)] == 0
 
diff --git a/Tests/test_file_libtiff.py b/Tests/test_file_libtiff.py
index 62f8719af..8fd89787b 100644
--- a/Tests/test_file_libtiff.py
+++ b/Tests/test_file_libtiff.py
@@ -11,7 +11,15 @@ from typing import Any, NamedTuple
 
 import pytest
 
-from PIL import Image, ImageFilter, ImageOps, TiffImagePlugin, TiffTags, features
+from PIL import (
+    Image,
+    ImageFile,
+    ImageFilter,
+    ImageOps,
+    TiffImagePlugin,
+    TiffTags,
+    features,
+)
 from PIL.TiffImagePlugin import OSUBFILETYPE, SAMPLEFORMAT, STRIPOFFSETS, SUBIFD
 
 from .helper import (
@@ -27,7 +35,7 @@ from .helper import (
 
 @skip_unless_feature("libtiff")
 class LibTiffTestCase:
-    def _assert_noerr(self, tmp_path: Path, im: TiffImagePlugin.TiffImageFile) -> None:
+    def _assert_noerr(self, tmp_path: Path, im: ImageFile.ImageFile) -> None:
         """Helper tests that assert basic sanity about the g4 tiff reading"""
         # 1 bit
         assert im.mode == "1"
@@ -36,6 +44,7 @@ class LibTiffTestCase:
         im.load()
         im.getdata()
 
+        assert isinstance(im, TiffImagePlugin.TiffImageFile)
         try:
             assert im._compression == "group4"
         except AttributeError:
@@ -157,6 +166,7 @@ class TestFileLibTiff(LibTiffTestCase):
         """Test metadata writing through libtiff"""
         f = str(tmp_path / "temp.tiff")
         with Image.open("Tests/images/hopper_g4.tif") as img:
+            assert isinstance(img, TiffImagePlugin.TiffImageFile)
             img.save(f, tiffinfo=img.tag)
 
             if legacy_api:
@@ -174,6 +184,7 @@ class TestFileLibTiff(LibTiffTestCase):
         ]
 
         with Image.open(f) as loaded:
+            assert isinstance(loaded, TiffImagePlugin.TiffImageFile)
             if legacy_api:
                 reloaded = loaded.tag.named()
             else:
@@ -216,6 +227,7 @@ class TestFileLibTiff(LibTiffTestCase):
         # Exclude ones that have special meaning
         # that we're already testing them
         with Image.open("Tests/images/hopper_g4.tif") as im:
+            assert isinstance(im, TiffImagePlugin.TiffImageFile)
             for tag in im.tag_v2:
                 try:
                     del core_items[tag]
@@ -321,6 +333,7 @@ class TestFileLibTiff(LibTiffTestCase):
             im.save(out, tiffinfo=tiffinfo)
 
             with Image.open(out) as reloaded:
+                assert isinstance(reloaded, TiffImagePlugin.TiffImageFile)
                 for tag, value in tiffinfo.items():
                     reloaded_value = reloaded.tag_v2[tag]
                     if (
@@ -353,12 +366,14 @@ class TestFileLibTiff(LibTiffTestCase):
     def test_osubfiletype(self, tmp_path: Path) -> None:
         outfile = str(tmp_path / "temp.tif")
         with Image.open("Tests/images/g4_orientation_6.tif") as im:
+            assert isinstance(im, TiffImagePlugin.TiffImageFile)
             im.tag_v2[OSUBFILETYPE] = 1
             im.save(outfile)
 
     def test_subifd(self, tmp_path: Path) -> None:
         outfile = str(tmp_path / "temp.tif")
         with Image.open("Tests/images/g4_orientation_6.tif") as im:
+            assert isinstance(im, TiffImagePlugin.TiffImageFile)
             im.tag_v2[SUBIFD] = 10000
 
             # Should not segfault
@@ -373,6 +388,7 @@ class TestFileLibTiff(LibTiffTestCase):
         hopper().save(out, tiffinfo={700: b"xmlpacket tag"})
 
         with Image.open(out) as reloaded:
+            assert isinstance(reloaded, TiffImagePlugin.TiffImageFile)
             if 700 in reloaded.tag_v2:
                 assert reloaded.tag_v2[700] == b"xmlpacket tag"
 
@@ -434,12 +450,14 @@ class TestFileLibTiff(LibTiffTestCase):
         """Tests String data in info directory"""
         test_file = "Tests/images/hopper_g4_500.tif"
         with Image.open(test_file) as orig:
-            out = str(tmp_path / "temp.tif")
+            assert isinstance(orig, TiffImagePlugin.TiffImageFile)
 
+            out = str(tmp_path / "temp.tif")
             orig.tag[269] = "temp.tif"
             orig.save(out)
 
         with Image.open(out) as reread:
+            assert isinstance(reread, TiffImagePlugin.TiffImageFile)
             assert "temp.tif" == reread.tag_v2[269]
             assert "temp.tif" == reread.tag[269][0]
 
@@ -462,8 +480,8 @@ class TestFileLibTiff(LibTiffTestCase):
         # test case from irc, how to do blur on b/w image
         # and save to compressed tif.
         out = str(tmp_path / "temp.tif")
-        with Image.open("Tests/images/pport_g4.tif") as im:
-            im = im.convert("L")
+        with Image.open("Tests/images/pport_g4.tif") as img:
+            im = img.convert("L")
 
         im = im.filter(ImageFilter.GaussianBlur(4))
         im.save(out, compression="tiff_adobe_deflate")
@@ -545,6 +563,7 @@ class TestFileLibTiff(LibTiffTestCase):
 
         with Image.open(out) as reloaded:
             # colormap/palette tag
+            assert isinstance(reloaded, TiffImagePlugin.TiffImageFile)
             assert len(reloaded.tag_v2[320]) == 768
 
     @pytest.mark.parametrize("compression", ("tiff_ccitt", "group3", "group4"))
@@ -556,8 +575,9 @@ class TestFileLibTiff(LibTiffTestCase):
             im.save(out, compression=compression)
 
     def test_fp_leak(self) -> None:
-        im: Image.Image | None = Image.open("Tests/images/hopper_g4_500.tif")
+        im: ImageFile.ImageFile | None = Image.open("Tests/images/hopper_g4_500.tif")
         assert im is not None
+        assert im.fp is not None
         fn = im.fp.fileno()
 
         os.fstat(fn)
@@ -576,6 +596,7 @@ class TestFileLibTiff(LibTiffTestCase):
         with Image.open("Tests/images/multipage.tiff") as im:
             # file is a multipage tiff,  10x10 green, 10x10 red, 20x20 blue
 
+            assert isinstance(im, TiffImagePlugin.TiffImageFile)
             im.seek(0)
             assert im.size == (10, 10)
             assert im.convert("RGB").getpixel((0, 0)) == (0, 128, 0)
@@ -595,6 +616,7 @@ class TestFileLibTiff(LibTiffTestCase):
         # issue #862
         monkeypatch.setattr(TiffImagePlugin, "READ_LIBTIFF", True)
         with Image.open("Tests/images/multipage.tiff") as im:
+            assert isinstance(im, TiffImagePlugin.TiffImageFile)
             frames = im.n_frames
             assert frames == 3
             for _ in range(frames):
@@ -614,6 +636,7 @@ class TestFileLibTiff(LibTiffTestCase):
     def test__next(self, monkeypatch: pytest.MonkeyPatch) -> None:
         monkeypatch.setattr(TiffImagePlugin, "READ_LIBTIFF", True)
         with Image.open("Tests/images/hopper.tif") as im:
+            assert isinstance(im, TiffImagePlugin.TiffImageFile)
             assert not im.tag.next
             im.load()
             assert not im.tag.next
@@ -694,21 +717,25 @@ class TestFileLibTiff(LibTiffTestCase):
         im.save(outfile, compression="jpeg")
 
         with Image.open(outfile) as reloaded:
+            assert isinstance(reloaded, TiffImagePlugin.TiffImageFile)
             assert reloaded.tag_v2[530] == (1, 1)
             assert reloaded.tag_v2[532] == (0, 255, 128, 255, 128, 255)
 
     def test_exif_ifd(self) -> None:
         out = io.BytesIO()
         with Image.open("Tests/images/tiff_adobe_deflate.tif") as im:
+            assert isinstance(im, TiffImagePlugin.TiffImageFile)
             assert im.tag_v2[34665] == 125456
             im.save(out, "TIFF")
 
             with Image.open(out) as reloaded:
+                assert isinstance(reloaded, TiffImagePlugin.TiffImageFile)
                 assert 34665 not in reloaded.tag_v2
 
             im.save(out, "TIFF", tiffinfo={34665: 125456})
 
         with Image.open(out) as reloaded:
+            assert isinstance(reloaded, TiffImagePlugin.TiffImageFile)
             if Image.core.libtiff_support_custom_tags:
                 assert reloaded.tag_v2[34665] == 125456
 
@@ -790,6 +817,8 @@ class TestFileLibTiff(LibTiffTestCase):
 
     def test_multipage_compression(self) -> None:
         with Image.open("Tests/images/compression.tif") as im:
+            assert isinstance(im, TiffImagePlugin.TiffImageFile)
+
             im.seek(0)
             assert im._compression == "tiff_ccitt"
             assert im.size == (10, 10)
@@ -1083,6 +1112,7 @@ class TestFileLibTiff(LibTiffTestCase):
         with Image.open("Tests/images/g4_orientation_1.tif") as base_im:
             for i in range(2, 9):
                 with Image.open("Tests/images/g4_orientation_" + str(i) + ".tif") as im:
+                    assert isinstance(im, TiffImagePlugin.TiffImageFile)
                     assert 274 in im.tag_v2
 
                     im.load()
@@ -1094,9 +1124,10 @@ class TestFileLibTiff(LibTiffTestCase):
         with Image.open("Tests/images/g4_orientation_1.tif") as base_im:
             for i in range(2, 9):
                 with Image.open("Tests/images/g4_orientation_" + str(i) + ".tif") as im:
-                    im = ImageOps.exif_transpose(im)
+                    transposed_im = ImageOps.exif_transpose(im)
+                    assert transposed_im is not None
 
-                    assert_image_similar(base_im, im, 0.7)
+                    assert_image_similar(base_im, transposed_im, 0.7)
 
     @pytest.mark.valgrind_known_error(reason="Backtrace in Python Core")
     def test_sampleformat_not_corrupted(self) -> None:
diff --git a/Tests/test_file_mic.py b/Tests/test_file_mic.py
index 9a6f13ea3..0706af4c0 100644
--- a/Tests/test_file_mic.py
+++ b/Tests/test_file_mic.py
@@ -22,19 +22,21 @@ def test_sanity() -> None:
 
         # Adjust for the gamma of 2.2 encoded into the file
         lut = ImagePalette.make_gamma_lut(1 / 2.2)
-        im = Image.merge("RGBA", [chan.point(lut) for chan in im.split()])
+        im1 = Image.merge("RGBA", [chan.point(lut) for chan in im.split()])
 
         im2 = hopper("RGBA")
-        assert_image_similar(im, im2, 10)
+        assert_image_similar(im1, im2, 10)
 
 
 def test_n_frames() -> None:
     with Image.open(TEST_FILE) as im:
+        assert isinstance(im, MicImagePlugin.MicImageFile)
         assert im.n_frames == 1
 
 
 def test_is_animated() -> None:
     with Image.open(TEST_FILE) as im:
+        assert isinstance(im, MicImagePlugin.MicImageFile)
         assert not im.is_animated
 
 
@@ -55,10 +57,11 @@ def test_seek() -> None:
 
 def test_close() -> None:
     with Image.open(TEST_FILE) as im:
-        pass
+        assert isinstance(im, MicImagePlugin.MicImageFile)
     assert im.ole.fp.closed
 
     im = Image.open(TEST_FILE)
+    assert isinstance(im, MicImagePlugin.MicImageFile)
     im.close()
     assert im.ole.fp.closed
 
diff --git a/Tests/test_file_mpo.py b/Tests/test_file_mpo.py
index e0f42a266..08618df61 100644
--- a/Tests/test_file_mpo.py
+++ b/Tests/test_file_mpo.py
@@ -6,7 +6,7 @@ from typing import Any
 
 import pytest
 
-from PIL import Image, ImageFile, MpoImagePlugin
+from PIL import Image, ImageFile, JpegImagePlugin, MpoImagePlugin
 
 from .helper import (
     assert_image_equal,
@@ -71,6 +71,7 @@ def test_context_manager() -> None:
 def test_app(test_file: str) -> None:
     # Test APP/COM reader (@PIL135)
     with Image.open(test_file) as im:
+        assert isinstance(im, MpoImagePlugin.MpoImageFile)
         assert im.applist[0][0] == "APP1"
         assert im.applist[1][0] == "APP2"
         assert (
@@ -110,9 +111,11 @@ def test_ignore_frame_size() -> None:
     # Ignore the different size of the second frame
     # since this is not a "Large Thumbnail" image
     with Image.open("Tests/images/ignore_frame_size.mpo") as im:
+        assert isinstance(im, MpoImagePlugin.MpoImageFile)
         assert im.size == (64, 64)
 
         im.seek(1)
+        assert im.mpinfo is not None
         assert (
             im.mpinfo[0xB002][1]["Attribute"]["MPType"]
             == "Multi-Frame Image: (Disparity)"
@@ -145,7 +148,9 @@ def test_reload_exif_after_seek() -> None:
 @pytest.mark.parametrize("test_file", test_files)
 def test_mp(test_file: str) -> None:
     with Image.open(test_file) as im:
+        assert isinstance(im, MpoImagePlugin.MpoImageFile)
         mpinfo = im._getmp()
+        assert mpinfo is not None
         assert mpinfo[45056] == b"0100"
         assert mpinfo[45057] == 2
 
@@ -154,7 +159,9 @@ def test_mp_offset() -> None:
     # This image has been manually hexedited to have an IFD offset of 10
     # in APP2 data, in contrast to normal 8
     with Image.open("Tests/images/sugarshack_ifd_offset.mpo") as im:
+        assert isinstance(im, MpoImagePlugin.MpoImageFile)
         mpinfo = im._getmp()
+        assert mpinfo is not None
         assert mpinfo[45056] == b"0100"
         assert mpinfo[45057] == 2
 
@@ -170,7 +177,9 @@ def test_mp_no_data() -> None:
 @pytest.mark.parametrize("test_file", test_files)
 def test_mp_attribute(test_file: str) -> None:
     with Image.open(test_file) as im:
+        assert isinstance(im, MpoImagePlugin.MpoImageFile)
         mpinfo = im._getmp()
+        assert mpinfo is not None
     for frame_number, mpentry in enumerate(mpinfo[0xB002]):
         mpattr = mpentry["Attribute"]
         if frame_number:
@@ -211,12 +220,14 @@ def test_seek(test_file: str) -> None:
 
 def test_n_frames() -> None:
     with Image.open("Tests/images/sugarshack.mpo") as im:
+        assert isinstance(im, MpoImagePlugin.MpoImageFile)
         assert im.n_frames == 2
         assert im.is_animated
 
 
 def test_eoferror() -> None:
     with Image.open("Tests/images/sugarshack.mpo") as im:
+        assert isinstance(im, MpoImagePlugin.MpoImageFile)
         n_frames = im.n_frames
 
         # Test seeking past the last frame
@@ -230,6 +241,8 @@ def test_eoferror() -> None:
 
 def test_adopt_jpeg() -> None:
     with Image.open("Tests/images/hopper.jpg") as im:
+        assert isinstance(im, JpegImagePlugin.JpegImageFile)
+
         with pytest.raises(ValueError):
             MpoImagePlugin.MpoImageFile.adopt(im)
 
@@ -267,6 +280,7 @@ def test_save(test_file: str) -> None:
 
 
 def test_save_all() -> None:
+    im: Image.Image
     for test_file in test_files:
         with Image.open(test_file) as im:
             im_reloaded = roundtrip(im, save_all=True)
diff --git a/Tests/test_file_png.py b/Tests/test_file_png.py
index 0abf9866f..7e43a35be 100644
--- a/Tests/test_file_png.py
+++ b/Tests/test_file_png.py
@@ -4,7 +4,7 @@ import re
 import sys
 import warnings
 import zlib
-from io import BytesIO
+from io import BytesIO, TextIOWrapper
 from pathlib import Path
 from types import ModuleType
 from typing import Any, cast
@@ -93,6 +93,7 @@ class TestFilePng:
 
         hopper("RGB").save(test_file)
 
+        im: Image.Image
         with Image.open(test_file) as im:
             im.load()
             assert im.mode == "RGB"
@@ -103,6 +104,8 @@ class TestFilePng:
         for mode in ["1", "L", "P", "RGB", "I", "I;16", "I;16B"]:
             im = hopper(mode)
             im.save(test_file)
+
+            reloaded: Image.Image
             with Image.open(test_file) as reloaded:
                 if mode in ("I", "I;16B"):
                     reloaded = reloaded.convert(mode)
@@ -225,11 +228,13 @@ class TestFilePng:
         test_file = "Tests/images/pil123p.png"
         with Image.open(test_file) as im:
             assert_image(im, "P", (162, 150))
-            im = im.convert("RGBA")
-        assert_image(im, "RGBA", (162, 150))
+            rgba_im = im.convert("RGBA")
+        assert_image(rgba_im, "RGBA", (162, 150))
 
         # image has 124 unique alpha values
-        assert len(im.getchannel("A").getcolors()) == 124
+        colors = rgba_im.getchannel("A").getcolors()
+        assert colors is not None
+        assert len(colors) == 124
 
     def test_load_transparent_rgb(self) -> None:
         test_file = "Tests/images/rgb_trns.png"
@@ -237,11 +242,13 @@ class TestFilePng:
             assert im.info["transparency"] == (0, 255, 52)
 
             assert_image(im, "RGB", (64, 64))
-            im = im.convert("RGBA")
-        assert_image(im, "RGBA", (64, 64))
+            rgba_im = im.convert("RGBA")
+        assert_image(rgba_im, "RGBA", (64, 64))
 
         # image has 876 transparent pixels
-        assert im.getchannel("A").getcolors()[0][0] == 876
+        colors = rgba_im.getchannel("A").getcolors()
+        assert colors is not None
+        assert colors[0][0] == 876
 
     def test_save_p_transparent_palette(self, tmp_path: Path) -> None:
         in_file = "Tests/images/pil123p.png"
@@ -258,11 +265,13 @@ class TestFilePng:
             assert len(im.info["transparency"]) == 256
 
             assert_image(im, "P", (162, 150))
-            im = im.convert("RGBA")
-        assert_image(im, "RGBA", (162, 150))
+            rgba_im = im.convert("RGBA")
+        assert_image(rgba_im, "RGBA", (162, 150))
 
         # image has 124 unique alpha values
-        assert len(im.getchannel("A").getcolors()) == 124
+        colors = rgba_im.getchannel("A").getcolors()
+        assert colors is not None
+        assert len(colors) == 124
 
     def test_save_p_single_transparency(self, tmp_path: Path) -> None:
         in_file = "Tests/images/p_trns_single.png"
@@ -279,13 +288,15 @@ class TestFilePng:
             assert im.info["transparency"] == 164
             assert im.getpixel((31, 31)) == 164
             assert_image(im, "P", (64, 64))
-            im = im.convert("RGBA")
-        assert_image(im, "RGBA", (64, 64))
+            rgba_im = im.convert("RGBA")
+        assert_image(rgba_im, "RGBA", (64, 64))
 
-        assert im.getpixel((31, 31)) == (0, 255, 52, 0)
+        assert rgba_im.getpixel((31, 31)) == (0, 255, 52, 0)
 
         # image has 876 transparent pixels
-        assert im.getchannel("A").getcolors()[0][0] == 876
+        colors = rgba_im.getchannel("A").getcolors()
+        assert colors is not None
+        assert colors[0][0] == 876
 
     def test_save_p_transparent_black(self, tmp_path: Path) -> None:
         # check if solid black image with full transparency
@@ -313,7 +324,9 @@ class TestFilePng:
                 assert im.info["transparency"] == 255
 
                 im_rgba = im.convert("RGBA")
-            assert im_rgba.getchannel("A").getcolors()[0][0] == num_transparent
+            colors = im_rgba.getchannel("A").getcolors()
+            assert colors is not None
+            assert colors[0][0] == num_transparent
 
             test_file = str(tmp_path / "temp.png")
             im.save(test_file)
@@ -324,7 +337,9 @@ class TestFilePng:
                 assert_image_equal(im, test_im)
 
             test_im_rgba = test_im.convert("RGBA")
-            assert test_im_rgba.getchannel("A").getcolors()[0][0] == num_transparent
+            colors = test_im_rgba.getchannel("A").getcolors()
+            assert colors is not None
+            assert colors[0][0] == num_transparent
 
     def test_save_rgb_single_transparency(self, tmp_path: Path) -> None:
         in_file = "Tests/images/caption_6_33_22.png"
@@ -578,6 +593,7 @@ class TestFilePng:
 
     def test_read_private_chunks(self) -> None:
         with Image.open("Tests/images/exif.png") as im:
+            assert isinstance(im, PngImagePlugin.PngImageFile)
             assert im.private_chunks == [(b"orNT", b"\x01")]
 
     def test_roundtrip_private_chunk(self) -> None:
@@ -600,6 +616,7 @@ class TestFilePng:
 
     def test_textual_chunks_after_idat(self) -> None:
         with Image.open("Tests/images/hopper.png") as im:
+            assert isinstance(im, PngImagePlugin.PngImageFile)
             assert "comment" in im.text
             for k, v in {
                 "date:create": "2014-09-04T09:37:08+03:00",
@@ -609,20 +626,24 @@ class TestFilePng:
 
         # Raises a SyntaxError in load_end
         with Image.open("Tests/images/broken_data_stream.png") as im:
+            assert isinstance(im, PngImagePlugin.PngImageFile)
             with pytest.raises(OSError):
                 assert isinstance(im.text, dict)
 
         # Raises a UnicodeDecodeError in load_end
         with Image.open("Tests/images/truncated_image.png") as im:
+            assert isinstance(im, PngImagePlugin.PngImageFile)
+
             # The file is truncated
             with pytest.raises(OSError):
-                im.text()
+                im.text
             ImageFile.LOAD_TRUNCATED_IMAGES = True
             assert isinstance(im.text, dict)
             ImageFile.LOAD_TRUNCATED_IMAGES = False
 
         # Raises an EOFError in load_end
         with Image.open("Tests/images/hopper_idat_after_image_end.png") as im:
+            assert isinstance(im, PngImagePlugin.PngImageFile)
             assert im.text == {"TXT": "VALUE", "ZIP": "VALUE"}
 
     def test_unknown_compression_method(self) -> None:
@@ -667,6 +688,9 @@ class TestFilePng:
         im.save(out, bits=4, save_all=save_all)
 
         with Image.open(out) as reloaded:
+            assert isinstance(reloaded, PngImagePlugin.PngImageFile)
+            assert reloaded.png is not None
+            assert reloaded.png.im_palette is not None
             assert len(reloaded.png.im_palette[1]) == 48
 
     def test_plte_length(self, tmp_path: Path) -> None:
@@ -677,6 +701,9 @@ class TestFilePng:
         im.save(str(tmp_path / "temp.png"))
 
         with Image.open(out) as reloaded:
+            assert isinstance(reloaded, PngImagePlugin.PngImageFile)
+            assert reloaded.png is not None
+            assert reloaded.png.im_palette is not None
             assert len(reloaded.png.im_palette[1]) == 3
 
     def test_getxmp(self) -> None:
@@ -698,13 +725,17 @@ class TestFilePng:
     def test_exif(self) -> None:
         # With an EXIF chunk
         with Image.open("Tests/images/exif.png") as im:
-            exif = im._getexif()
-        assert exif[274] == 1
+            assert isinstance(im, PngImagePlugin.PngImageFile)
+            exif_data = im._getexif()
+        assert exif_data is not None
+        assert exif_data[274] == 1
 
         # With an ImageMagick zTXt chunk
         with Image.open("Tests/images/exif_imagemagick.png") as im:
-            exif = im._getexif()
-            assert exif[274] == 1
+            assert isinstance(im, PngImagePlugin.PngImageFile)
+            exif_data = im._getexif()
+            assert exif_data is not None
+            assert exif_data[274] == 1
 
             # Assert that info still can be extracted
             # when the image is no longer a PngImageFile instance
@@ -713,8 +744,10 @@ class TestFilePng:
 
         # With a tEXt chunk
         with Image.open("Tests/images/exif_text.png") as im:
-            exif = im._getexif()
-        assert exif[274] == 1
+            assert isinstance(im, PngImagePlugin.PngImageFile)
+            exif_data = im._getexif()
+        assert exif_data is not None
+        assert exif_data[274] == 1
 
         # With XMP tags
         with Image.open("Tests/images/xmp_tags_orientation.png") as im:
@@ -728,6 +761,7 @@ class TestFilePng:
             im.save(test_file)
 
         with Image.open(test_file) as reloaded:
+            assert isinstance(reloaded, PngImagePlugin.PngImageFile)
             assert reloaded._getexif() is None
 
         # Test passing in exif
@@ -735,7 +769,9 @@ class TestFilePng:
             im.save(test_file, exif=im.getexif())
 
         with Image.open(test_file) as reloaded:
+            assert isinstance(reloaded, PngImagePlugin.PngImageFile)
             exif = reloaded._getexif()
+        assert exif is not None
         assert exif[274] == 1
 
     @mark_if_feature_version(
@@ -747,7 +783,9 @@ class TestFilePng:
             im.save(test_file, exif=im.getexif())
 
         with Image.open(test_file) as reloaded:
+            assert isinstance(reloaded, PngImagePlugin.PngImageFile)
             exif = reloaded._getexif()
+        assert exif is not None
         assert exif[305] == "Adobe Photoshop CS Macintosh"
 
     def test_exif_argument(self, tmp_path: Path) -> None:
@@ -773,10 +811,8 @@ class TestFilePng:
     def test_save_stdout(self, buffer: bool) -> None:
         old_stdout = sys.stdout
 
-        class MyStdOut:
-            buffer = BytesIO()
-
-        mystdout: MyStdOut | BytesIO = MyStdOut() if buffer else BytesIO()
+        b = BytesIO()
+        mystdout: TextIOWrapper | BytesIO = TextIOWrapper(b) if buffer else b
 
         sys.stdout = mystdout
 
@@ -786,9 +822,7 @@ class TestFilePng:
         # Reset stdout
         sys.stdout = old_stdout
 
-        if isinstance(mystdout, MyStdOut):
-            mystdout = mystdout.buffer
-        with Image.open(mystdout) as reloaded:
+        with Image.open(b) as reloaded:
             assert_image_equal_tofile(reloaded, TEST_PNG_FILE)
 
     def test_truncated_end_chunk(self) -> None:
diff --git a/Tests/test_file_ppm.py b/Tests/test_file_ppm.py
index fb08d613a..a7e523013 100644
--- a/Tests/test_file_ppm.py
+++ b/Tests/test_file_ppm.py
@@ -1,7 +1,7 @@
 from __future__ import annotations
 
 import sys
-from io import BytesIO
+from io import BytesIO, TextIOWrapper
 from pathlib import Path
 
 import pytest
@@ -79,6 +79,7 @@ def test_arbitrary_maxval(
         assert im.mode == mode
 
         px = im.load()
+        assert px is not None
         assert tuple(px[x, 0] for x in range(3)) == pixels
 
 
@@ -370,10 +371,8 @@ def test_mimetypes(tmp_path: Path) -> None:
 def test_save_stdout(buffer: bool) -> None:
     old_stdout = sys.stdout
 
-    class MyStdOut:
-        buffer = BytesIO()
-
-    mystdout: MyStdOut | BytesIO = MyStdOut() if buffer else BytesIO()
+    b = BytesIO()
+    mystdout: TextIOWrapper | BytesIO = TextIOWrapper(b) if buffer else b
 
     sys.stdout = mystdout
 
@@ -383,7 +382,5 @@ def test_save_stdout(buffer: bool) -> None:
     # Reset stdout
     sys.stdout = old_stdout
 
-    if isinstance(mystdout, MyStdOut):
-        mystdout = mystdout.buffer
-    with Image.open(mystdout) as reloaded:
+    with Image.open(b) as reloaded:
         assert_image_equal_tofile(reloaded, TEST_FILE)
diff --git a/Tests/test_file_psd.py b/Tests/test_file_psd.py
index e6c79e40b..00eba589a 100644
--- a/Tests/test_file_psd.py
+++ b/Tests/test_file_psd.py
@@ -55,17 +55,21 @@ def test_invalid_file() -> None:
 
 def test_n_frames() -> None:
     with Image.open("Tests/images/hopper_merged.psd") as im:
+        assert isinstance(im, PsdImagePlugin.PsdImageFile)
         assert im.n_frames == 1
         assert not im.is_animated
 
     for path in [test_file, "Tests/images/negative_layer_count.psd"]:
         with Image.open(path) as im:
+            assert isinstance(im, PsdImagePlugin.PsdImageFile)
             assert im.n_frames == 2
             assert im.is_animated
 
 
 def test_eoferror() -> None:
     with Image.open(test_file) as im:
+        assert isinstance(im, PsdImagePlugin.PsdImageFile)
+
         # PSD seek index starts at 1 rather than 0
         n_frames = im.n_frames + 1
 
@@ -115,11 +119,13 @@ def test_rgba() -> None:
 
 def test_negative_top_left_layer() -> None:
     with Image.open("Tests/images/negative_top_left_layer.psd") as im:
+        assert isinstance(im, PsdImagePlugin.PsdImageFile)
         assert im.layers[0][2] == (-50, -50, 50, 50)
 
 
 def test_layer_skip() -> None:
     with Image.open("Tests/images/five_channels.psd") as im:
+        assert isinstance(im, PsdImagePlugin.PsdImageFile)
         assert im.n_frames == 1
 
 
@@ -171,5 +177,6 @@ def test_crashes(test_file: str, raises: type[Exception]) -> None:
 def test_layer_crashes(test_file: str) -> None:
     with open(test_file, "rb") as f:
         with Image.open(f) as im:
+            assert isinstance(im, PsdImagePlugin.PsdImageFile)
             with pytest.raises(SyntaxError):
                 im.layers
diff --git a/Tests/test_file_spider.py b/Tests/test_file_spider.py
index 66c88e9d8..0155c1366 100644
--- a/Tests/test_file_spider.py
+++ b/Tests/test_file_spider.py
@@ -92,6 +92,7 @@ def test_tell() -> None:
 
 def test_n_frames() -> None:
     with Image.open(TEST_FILE) as im:
+        assert isinstance(im, SpiderImagePlugin.SpiderImageFile)
         assert im.n_frames == 1
         assert not im.is_animated
 
diff --git a/Tests/test_file_tga.py b/Tests/test_file_tga.py
index a03a6a6e1..25dbeaea6 100644
--- a/Tests/test_file_tga.py
+++ b/Tests/test_file_tga.py
@@ -72,6 +72,7 @@ def test_palette_depth_8(tmp_path: Path) -> None:
 
 def test_palette_depth_16(tmp_path: Path) -> None:
     with Image.open("Tests/images/p_16.tga") as im:
+        assert im.palette is not None
         assert im.palette.mode == "RGBA"
         assert_image_equal_tofile(im.convert("RGBA"), "Tests/images/p_16.png")
 
@@ -213,10 +214,18 @@ def test_save_orientation(tmp_path: Path) -> None:
 def test_horizontal_orientations() -> None:
     # These images have been manually hexedited to have the relevant orientations
     with Image.open("Tests/images/rgb32rle_top_right.tga") as im:
-        assert im.load()[90, 90][:3] == (0, 0, 0)
+        px = im.load()
+        assert px is not None
+        value = px[90, 90]
+        assert isinstance(value, tuple)
+        assert value[:3] == (0, 0, 0)
 
     with Image.open("Tests/images/rgb32rle_bottom_right.tga") as im:
-        assert im.load()[90, 90][:3] == (0, 255, 0)
+        px = im.load()
+        assert px is not None
+        value = px[90, 90]
+        assert isinstance(value, tuple)
+        assert value[:3] == (0, 255, 0)
 
 
 def test_save_rle(tmp_path: Path) -> None:
@@ -259,13 +268,17 @@ def test_save_l_transparency(tmp_path: Path) -> None:
     in_file = "Tests/images/la.tga"
     with Image.open(in_file) as im:
         assert im.mode == "LA"
-        assert im.getchannel("A").getcolors()[0][0] == num_transparent
+        colors = im.getchannel("A").getcolors()
+        assert colors is not None
+        assert colors[0][0] == num_transparent
 
         out = str(tmp_path / "temp.tga")
         im.save(out)
 
     with Image.open(out) as test_im:
         assert test_im.mode == "LA"
-        assert test_im.getchannel("A").getcolors()[0][0] == num_transparent
+        colors = test_im.getchannel("A").getcolors()
+        assert colors is not None
+        assert colors[0][0] == num_transparent
 
         assert_image_equal(im, test_im)
diff --git a/Tests/test_file_tiff.py b/Tests/test_file_tiff.py
index 190f83f40..c00178bff 100644
--- a/Tests/test_file_tiff.py
+++ b/Tests/test_file_tiff.py
@@ -9,7 +9,13 @@ from types import ModuleType
 
 import pytest
 
-from PIL import Image, ImageFile, TiffImagePlugin, UnidentifiedImageError
+from PIL import (
+    Image,
+    ImageFile,
+    JpegImagePlugin,
+    TiffImagePlugin,
+    UnidentifiedImageError,
+)
 from PIL.TiffImagePlugin import RESOLUTION_UNIT, X_RESOLUTION, Y_RESOLUTION
 
 from .helper import (
@@ -108,6 +114,8 @@ class TestFileTiff:
             assert_image_equal_tofile(im, "Tests/images/hopper.tif")
 
         with Image.open("Tests/images/hopper_bigtiff.tif") as im:
+            assert isinstance(im, TiffImagePlugin.TiffImageFile)
+
             # multistrip support not yet implemented
             del im.tag_v2[273]
 
@@ -127,6 +135,8 @@ class TestFileTiff:
     def test_xyres_tiff(self) -> None:
         filename = "Tests/images/pil168.tif"
         with Image.open(filename) as im:
+            assert isinstance(im, TiffImagePlugin.TiffImageFile)
+
             # legacy api
             assert isinstance(im.tag[X_RESOLUTION][0], tuple)
             assert isinstance(im.tag[Y_RESOLUTION][0], tuple)
@@ -140,6 +150,8 @@ class TestFileTiff:
     def test_xyres_fallback_tiff(self) -> None:
         filename = "Tests/images/compression.tif"
         with Image.open(filename) as im:
+            assert isinstance(im, TiffImagePlugin.TiffImageFile)
+
             # v2 api
             assert isinstance(im.tag_v2[X_RESOLUTION], TiffImagePlugin.IFDRational)
             assert isinstance(im.tag_v2[Y_RESOLUTION], TiffImagePlugin.IFDRational)
@@ -154,6 +166,8 @@ class TestFileTiff:
     def test_int_resolution(self) -> None:
         filename = "Tests/images/pil168.tif"
         with Image.open(filename) as im:
+            assert isinstance(im, TiffImagePlugin.TiffImageFile)
+
             # Try to read a file where X,Y_RESOLUTION are ints
             im.tag_v2[X_RESOLUTION] = 71
             im.tag_v2[Y_RESOLUTION] = 71
@@ -168,6 +182,7 @@ class TestFileTiff:
         with Image.open(
             "Tests/images/hopper_float_dpi_" + str(resolution_unit) + ".tif"
         ) as im:
+            assert isinstance(im, TiffImagePlugin.TiffImageFile)
             assert im.tag_v2.get(RESOLUTION_UNIT) == resolution_unit
             assert im.info["dpi"] == (dpi, dpi)
 
@@ -185,6 +200,7 @@ class TestFileTiff:
         with Image.open("Tests/images/10ct_32bit_128.tiff") as im:
             im.save(b, format="tiff", resolution=123.45)
         with Image.open(b) as im:
+            assert isinstance(im, TiffImagePlugin.TiffImageFile)
             assert im.tag_v2[X_RESOLUTION] == 123.45
             assert im.tag_v2[Y_RESOLUTION] == 123.45
 
@@ -200,10 +216,12 @@ class TestFileTiff:
         TiffImagePlugin.PREFIXES.pop()
 
     def test_bad_exif(self) -> None:
-        with Image.open("Tests/images/hopper_bad_exif.jpg") as i:
+        with Image.open("Tests/images/hopper_bad_exif.jpg") as im:
+            assert isinstance(im, JpegImagePlugin.JpegImageFile)
+
             # Should not raise struct.error.
             with pytest.warns(UserWarning):
-                i._getexif()
+                im._getexif()
 
     def test_save_rgba(self, tmp_path: Path) -> None:
         im = hopper("RGBA")
@@ -294,11 +312,13 @@ class TestFileTiff:
     )
     def test_n_frames(self, path: str, n_frames: int) -> None:
         with Image.open(path) as im:
+            assert isinstance(im, TiffImagePlugin.TiffImageFile)
             assert im.n_frames == n_frames
             assert im.is_animated == (n_frames != 1)
 
     def test_eoferror(self) -> None:
         with Image.open("Tests/images/multipage-lastframe.tif") as im:
+            assert isinstance(im, TiffImagePlugin.TiffImageFile)
             n_frames = im.n_frames
 
             # Test seeking past the last frame
@@ -342,20 +362,24 @@ class TestFileTiff:
     def test_frame_order(self) -> None:
         # A frame can't progress to itself after reading
         with Image.open("Tests/images/multipage_single_frame_loop.tiff") as im:
+            assert isinstance(im, TiffImagePlugin.TiffImageFile)
             assert im.n_frames == 1
 
         # A frame can't progress to a frame that has already been read
         with Image.open("Tests/images/multipage_multiple_frame_loop.tiff") as im:
+            assert isinstance(im, TiffImagePlugin.TiffImageFile)
             assert im.n_frames == 2
 
         # Frames don't have to be in sequence
         with Image.open("Tests/images/multipage_out_of_order.tiff") as im:
+            assert isinstance(im, TiffImagePlugin.TiffImageFile)
             assert im.n_frames == 3
 
     def test___str__(self) -> None:
         filename = "Tests/images/pil136.tiff"
         with Image.open(filename) as im:
             # Act
+            assert isinstance(im, TiffImagePlugin.TiffImageFile)
             ret = str(im.ifd)
 
             # Assert
@@ -365,6 +389,8 @@ class TestFileTiff:
         # Arrange
         filename = "Tests/images/pil136.tiff"
         with Image.open(filename) as im:
+            assert isinstance(im, TiffImagePlugin.TiffImageFile)
+
             # v2 interface
             v2_tags = {
                 256: 55,
@@ -404,6 +430,7 @@ class TestFileTiff:
     def test__delitem__(self) -> None:
         filename = "Tests/images/pil136.tiff"
         with Image.open(filename) as im:
+            assert isinstance(im, TiffImagePlugin.TiffImageFile)
             len_before = len(dict(im.ifd))
             del im.ifd[256]
             len_after = len(dict(im.ifd))
@@ -436,6 +463,7 @@ class TestFileTiff:
 
     def test_ifd_tag_type(self) -> None:
         with Image.open("Tests/images/ifd_tag_type.tiff") as im:
+            assert isinstance(im, TiffImagePlugin.TiffImageFile)
             assert 0x8825 in im.tag_v2
 
     def test_exif(self, tmp_path: Path) -> None:
@@ -524,6 +552,7 @@ class TestFileTiff:
         im = hopper(mode)
         im.save(filename, tiffinfo={262: 0})
         with Image.open(filename) as reloaded:
+            assert isinstance(reloaded, TiffImagePlugin.TiffImageFile)
             assert reloaded.tag_v2[262] == 0
             assert_image_equal(im, reloaded)
 
@@ -602,6 +631,8 @@ class TestFileTiff:
         filename = str(tmp_path / "temp.tif")
         hopper("RGB").save(filename, "TIFF", **kwargs)
         with Image.open(filename) as im:
+            assert isinstance(im, TiffImagePlugin.TiffImageFile)
+
             # legacy interface
             assert im.tag[X_RESOLUTION][0][0] == 72
             assert im.tag[Y_RESOLUTION][0][0] == 36
@@ -676,6 +707,7 @@ class TestFileTiff:
     def test_planar_configuration_save(self, tmp_path: Path) -> None:
         infile = "Tests/images/tiff_tiled_planar_raw.tif"
         with Image.open(infile) as im:
+            assert isinstance(im, TiffImagePlugin.TiffImageFile)
             assert im._planar_configuration == 2
 
             outfile = str(tmp_path / "temp.tif")
@@ -703,12 +735,13 @@ class TestFileTiff:
 
     def test_tiff_save_all(self) -> None:
         mp = BytesIO()
-        with Image.open("Tests/images/multipage.tiff") as im:
-            im.save(mp, format="tiff", save_all=True)
+        with Image.open("Tests/images/multipage.tiff") as img:
+            img.save(mp, format="tiff", save_all=True)
 
         mp.seek(0, os.SEEK_SET)
-        with Image.open(mp) as im:
-            assert im.n_frames == 3
+        with Image.open(mp) as img:
+            assert isinstance(img, TiffImagePlugin.TiffImageFile)
+            assert img.n_frames == 3
 
         # Test appending images
         mp = BytesIO()
@@ -718,6 +751,7 @@ class TestFileTiff:
 
         mp.seek(0, os.SEEK_SET)
         with Image.open(mp) as reread:
+            assert isinstance(reread, TiffImagePlugin.TiffImageFile)
             assert reread.n_frames == 3
 
         # Test appending using a generator
@@ -729,6 +763,7 @@ class TestFileTiff:
 
         mp.seek(0, os.SEEK_SET)
         with Image.open(mp) as reread:
+            assert isinstance(reread, TiffImagePlugin.TiffImageFile)
             assert reread.n_frames == 3
 
     def test_saving_icc_profile(self, tmp_path: Path) -> None:
@@ -792,6 +827,7 @@ class TestFileTiff:
 
     def test_get_photoshop_blocks(self) -> None:
         with Image.open("Tests/images/lab.tif") as im:
+            assert isinstance(im, TiffImagePlugin.TiffImageFile)
             assert list(im.get_photoshop_blocks().keys()) == [
                 1061,
                 1002,
@@ -846,6 +882,7 @@ class TestFileTiff:
 
         im = Image.open(tmpfile)
         fp = im.fp
+        assert fp is not None
         assert not fp.closed
         im.load()
         assert fp.closed
@@ -859,6 +896,7 @@ class TestFileTiff:
         with open(tmpfile, "rb") as f:
             im = Image.open(f)
             fp = im.fp
+            assert fp is not None
             assert not fp.closed
             im.load()
             assert not fp.closed
@@ -910,8 +948,9 @@ class TestFileTiffW32:
             im.save(tmpfile)
 
         im = Image.open(tmpfile)
+        assert im.fp is not None
+        assert not im.fp.closed
         fp = im.fp
-        assert not fp.closed
         with pytest.raises(OSError):
             os.remove(tmpfile)
         im.load()
diff --git a/Tests/test_file_tiff_metadata.py b/Tests/test_file_tiff_metadata.py
index 1e0310001..c131e16f4 100644
--- a/Tests/test_file_tiff_metadata.py
+++ b/Tests/test_file_tiff_metadata.py
@@ -61,6 +61,7 @@ def test_rt_metadata(tmp_path: Path) -> None:
     img.save(f, tiffinfo=info)
 
     with Image.open(f) as loaded:
+        assert isinstance(loaded, TiffImagePlugin.TiffImageFile)
         assert loaded.tag[ImageJMetaDataByteCounts] == (len(bin_data),)
         assert loaded.tag_v2[ImageJMetaDataByteCounts] == (len(bin_data),)
 
@@ -80,12 +81,14 @@ def test_rt_metadata(tmp_path: Path) -> None:
     info[ImageJMetaDataByteCounts] = (8, len(bin_data) - 8)
     img.save(f, tiffinfo=info)
     with Image.open(f) as loaded:
+        assert isinstance(loaded, TiffImagePlugin.TiffImageFile)
         assert loaded.tag[ImageJMetaDataByteCounts] == (8, len(bin_data) - 8)
         assert loaded.tag_v2[ImageJMetaDataByteCounts] == (8, len(bin_data) - 8)
 
 
 def test_read_metadata() -> None:
     with Image.open("Tests/images/hopper_g4.tif") as img:
+        assert isinstance(img, TiffImagePlugin.TiffImageFile)
         assert {
             "YResolution": IFDRational(4294967295, 113653537),
             "PlanarConfiguration": 1,
@@ -128,6 +131,8 @@ def test_read_metadata() -> None:
 def test_write_metadata(tmp_path: Path) -> None:
     """Test metadata writing through the python code"""
     with Image.open("Tests/images/hopper.tif") as img:
+        assert isinstance(img, TiffImagePlugin.TiffImageFile)
+
         f = str(tmp_path / "temp.tiff")
         del img.tag[278]
         img.save(f, tiffinfo=img.tag)
@@ -135,6 +140,7 @@ def test_write_metadata(tmp_path: Path) -> None:
         original = img.tag_v2.named()
 
     with Image.open(f) as loaded:
+        assert isinstance(loaded, TiffImagePlugin.TiffImageFile)
         reloaded = loaded.tag_v2.named()
 
     ignored = ["StripByteCounts", "RowsPerStrip", "PageNumber", "StripOffsets"]
@@ -165,19 +171,21 @@ def test_write_metadata(tmp_path: Path) -> None:
 def test_change_stripbytecounts_tag_type(tmp_path: Path) -> None:
     out = str(tmp_path / "temp.tiff")
     with Image.open("Tests/images/hopper.tif") as im:
+        assert isinstance(im, TiffImagePlugin.TiffImageFile)
         info = im.tag_v2
         del info[278]
 
         # Resize the image so that STRIPBYTECOUNTS will be larger than a SHORT
-        im = im.resize((500, 500))
-        info[TiffImagePlugin.IMAGEWIDTH] = im.width
+        resized_im = im.resize((500, 500))
+        info[TiffImagePlugin.IMAGEWIDTH] = resized_im.width
 
         # STRIPBYTECOUNTS can be a SHORT or a LONG
         info.tagtype[TiffImagePlugin.STRIPBYTECOUNTS] = TiffTags.SHORT
 
-        im.save(out, tiffinfo=info)
+        resized_im.save(out, tiffinfo=info)
 
     with Image.open(out) as reloaded:
+        assert isinstance(reloaded, TiffImagePlugin.TiffImageFile)
         assert reloaded.tag_v2.tagtype[TiffImagePlugin.STRIPBYTECOUNTS] == TiffTags.LONG
 
 
@@ -208,6 +216,7 @@ def test_writing_other_types_to_ascii(
     im.save(out, tiffinfo=info)
 
     with Image.open(out) as reloaded:
+        assert isinstance(reloaded, TiffImagePlugin.TiffImageFile)
         assert reloaded.tag_v2[271] == expected
 
 
@@ -225,6 +234,7 @@ def test_writing_other_types_to_bytes(value: int | IFDRational, tmp_path: Path)
     im.save(out, tiffinfo=info)
 
     with Image.open(out) as reloaded:
+        assert isinstance(reloaded, TiffImagePlugin.TiffImageFile)
         assert reloaded.tag_v2[700] == b"\x01"
 
 
@@ -244,6 +254,7 @@ def test_writing_other_types_to_undefined(
     im.save(out, tiffinfo=info)
 
     with Image.open(out) as reloaded:
+        assert isinstance(reloaded, TiffImagePlugin.TiffImageFile)
         assert reloaded.tag_v2[33723] == b"1"
 
 
@@ -288,6 +299,7 @@ def test_iccprofile_binary() -> None:
     # but probably won't be able to save it.
 
     with Image.open("Tests/images/hopper.iccprofile_binary.tif") as im:
+        assert isinstance(im, TiffImagePlugin.TiffImageFile)
         assert im.tag_v2.tagtype[34675] == 1
         assert im.info["icc_profile"]
 
@@ -313,6 +325,7 @@ def test_exif_div_zero(tmp_path: Path) -> None:
     im.save(out, tiffinfo=info, compression="raw")
 
     with Image.open(out) as reloaded:
+        assert isinstance(reloaded, TiffImagePlugin.TiffImageFile)
         assert 0 == reloaded.tag_v2[41988].numerator
         assert 0 == reloaded.tag_v2[41988].denominator
 
@@ -332,6 +345,7 @@ def test_ifd_unsigned_rational(tmp_path: Path) -> None:
     im.save(out, tiffinfo=info, compression="raw")
 
     with Image.open(out) as reloaded:
+        assert isinstance(reloaded, TiffImagePlugin.TiffImageFile)
         assert max_long == reloaded.tag_v2[41493].numerator
         assert 1 == reloaded.tag_v2[41493].denominator
 
@@ -344,6 +358,7 @@ def test_ifd_unsigned_rational(tmp_path: Path) -> None:
     im.save(out, tiffinfo=info, compression="raw")
 
     with Image.open(out) as reloaded:
+        assert isinstance(reloaded, TiffImagePlugin.TiffImageFile)
         assert max_long == reloaded.tag_v2[41493].numerator
         assert 1 == reloaded.tag_v2[41493].denominator
 
@@ -362,6 +377,7 @@ def test_ifd_signed_rational(tmp_path: Path) -> None:
     im.save(out, tiffinfo=info, compression="raw")
 
     with Image.open(out) as reloaded:
+        assert isinstance(reloaded, TiffImagePlugin.TiffImageFile)
         assert numerator == reloaded.tag_v2[37380].numerator
         assert denominator == reloaded.tag_v2[37380].denominator
 
@@ -374,6 +390,7 @@ def test_ifd_signed_rational(tmp_path: Path) -> None:
     im.save(out, tiffinfo=info, compression="raw")
 
     with Image.open(out) as reloaded:
+        assert isinstance(reloaded, TiffImagePlugin.TiffImageFile)
         assert numerator == reloaded.tag_v2[37380].numerator
         assert denominator == reloaded.tag_v2[37380].denominator
 
@@ -387,6 +404,7 @@ def test_ifd_signed_rational(tmp_path: Path) -> None:
     im.save(out, tiffinfo=info, compression="raw")
 
     with Image.open(out) as reloaded:
+        assert isinstance(reloaded, TiffImagePlugin.TiffImageFile)
         assert 2**31 - 1 == reloaded.tag_v2[37380].numerator
         assert -1 == reloaded.tag_v2[37380].denominator
 
@@ -401,6 +419,7 @@ def test_ifd_signed_long(tmp_path: Path) -> None:
     im.save(out, tiffinfo=info, compression="raw")
 
     with Image.open(out) as reloaded:
+        assert isinstance(reloaded, TiffImagePlugin.TiffImageFile)
         assert reloaded.tag_v2[37000] == -60000
 
 
@@ -421,11 +440,13 @@ def test_empty_values() -> None:
 
 def test_photoshop_info(tmp_path: Path) -> None:
     with Image.open("Tests/images/issue_2278.tif") as im:
+        assert isinstance(im, TiffImagePlugin.TiffImageFile)
         assert len(im.tag_v2[34377]) == 70
         assert isinstance(im.tag_v2[34377], bytes)
         out = str(tmp_path / "temp.tiff")
         im.save(out)
     with Image.open(out) as reloaded:
+        assert isinstance(reloaded, TiffImagePlugin.TiffImageFile)
         assert len(reloaded.tag_v2[34377]) == 70
         assert isinstance(reloaded.tag_v2[34377], bytes)
 
diff --git a/Tests/test_file_wal.py b/Tests/test_file_wal.py
index b34975e83..bd1036712 100644
--- a/Tests/test_file_wal.py
+++ b/Tests/test_file_wal.py
@@ -21,7 +21,9 @@ def test_open() -> None:
 
 def test_load() -> None:
     with WalImageFile.open(TEST_FILE) as im:
-        assert im.load()[0, 0] == 122
+        px = im.load()
+        assert px is not None
+        assert px[0, 0] == 122
 
         # Test again now that it has already been loaded once
-        assert im.load()[0, 0] == 122
+        assert px[0, 0] == 122
diff --git a/Tests/test_file_webp.py b/Tests/test_file_webp.py
index e75e3ddd2..f305dbb95 100644
--- a/Tests/test_file_webp.py
+++ b/Tests/test_file_webp.py
@@ -218,6 +218,7 @@ class TestFileWebp:
         # Save P mode GIF with background
         with Image.open("Tests/images/chi.gif") as im:
             original_value = im.convert("RGB").getpixel((1, 1))
+            assert isinstance(original_value, tuple)
 
             # Save as WEBP
             out_webp = str(tmp_path / "temp.webp")
@@ -230,6 +231,7 @@ class TestFileWebp:
 
         with Image.open(out_gif) as reread:
             reread_value = reread.convert("RGB").getpixel((1, 1))
+        assert isinstance(reread_value, tuple)
         difference = sum(abs(original_value[i] - reread_value[i]) for i in range(0, 3))
         assert difference < 5
 
diff --git a/Tests/test_file_webp_animated.py b/Tests/test_file_webp_animated.py
index 967a0aae8..9035d9057 100644
--- a/Tests/test_file_webp_animated.py
+++ b/Tests/test_file_webp_animated.py
@@ -6,7 +6,7 @@ from pathlib import Path
 import pytest
 from packaging.version import parse as parse_version
 
-from PIL import Image, features
+from PIL import GifImagePlugin, Image, WebPImagePlugin, features
 
 from .helper import (
     assert_image_equal,
@@ -22,10 +22,12 @@ def test_n_frames() -> None:
     """Ensure that WebP format sets n_frames and is_animated attributes correctly."""
 
     with Image.open("Tests/images/hopper.webp") as im:
+        assert isinstance(im, WebPImagePlugin.WebPImageFile)
         assert im.n_frames == 1
         assert not im.is_animated
 
     with Image.open("Tests/images/iss634.webp") as im:
+        assert isinstance(im, WebPImagePlugin.WebPImageFile)
         assert im.n_frames == 42
         assert im.is_animated
 
@@ -37,11 +39,13 @@ def test_write_animation_L(tmp_path: Path) -> None:
     """
 
     with Image.open("Tests/images/iss634.gif") as orig:
+        assert isinstance(orig, GifImagePlugin.GifImageFile)
         assert orig.n_frames > 1
 
         temp_file = str(tmp_path / "temp.webp")
         orig.save(temp_file, save_all=True)
         with Image.open(temp_file) as im:
+            assert isinstance(im, WebPImagePlugin.WebPImageFile)
             assert im.n_frames == orig.n_frames
 
             # Compare first and last frames to the original animated GIF
@@ -69,6 +73,7 @@ def test_write_animation_RGB(tmp_path: Path) -> None:
 
     def check(temp_file: str) -> None:
         with Image.open(temp_file) as im:
+            assert isinstance(im, WebPImagePlugin.WebPImageFile)
             assert im.n_frames == 2
 
             # Compare first frame to original
@@ -127,6 +132,7 @@ def test_timestamp_and_duration(tmp_path: Path) -> None:
             )
 
     with Image.open(temp_file) as im:
+        assert isinstance(im, WebPImagePlugin.WebPImageFile)
         assert im.n_frames == 5
         assert im.is_animated
 
@@ -170,6 +176,7 @@ def test_seeking(tmp_path: Path) -> None:
             )
 
     with Image.open(temp_file) as im:
+        assert isinstance(im, WebPImagePlugin.WebPImageFile)
         assert im.n_frames == 5
         assert im.is_animated
 
diff --git a/Tests/test_file_webp_metadata.py b/Tests/test_file_webp_metadata.py
index d9a834c75..6ef9c34e3 100644
--- a/Tests/test_file_webp_metadata.py
+++ b/Tests/test_file_webp_metadata.py
@@ -6,7 +6,7 @@ from types import ModuleType
 
 import pytest
 
-from PIL import Image
+from PIL import Image, WebPImagePlugin
 
 from .helper import mark_if_feature_version, skip_unless_feature
 
@@ -22,11 +22,13 @@ except ImportError:
 def test_read_exif_metadata() -> None:
     file_path = "Tests/images/flower.webp"
     with Image.open(file_path) as image:
+        assert isinstance(image, WebPImagePlugin.WebPImageFile)
         assert image.format == "WEBP"
         exif_data = image.info.get("exif", None)
         assert exif_data
 
         exif = image._getexif()
+        assert exif is not None
 
         # Camera make
         assert exif[271] == "Canon"
@@ -110,6 +112,7 @@ def test_read_no_exif() -> None:
 
     test_buffer.seek(0)
     with Image.open(test_buffer) as webp_image:
+        assert isinstance(webp_image, WebPImagePlugin.WebPImageFile)
         assert not webp_image._getexif()
 
 
diff --git a/Tests/test_file_wmf.py b/Tests/test_file_wmf.py
index 79e707263..49e9c2c23 100644
--- a/Tests/test_file_wmf.py
+++ b/Tests/test_file_wmf.py
@@ -31,7 +31,9 @@ def test_load_raw() -> None:
 def test_load() -> None:
     with Image.open("Tests/images/drawing.emf") as im:
         if hasattr(Image.core, "drawwmf"):
-            assert im.load()[0, 0] == (255, 255, 255)
+            px = im.load()
+            assert px is not None
+            assert px[0, 0] == (255, 255, 255)
 
 
 def test_register_handler(tmp_path: Path) -> None:
@@ -64,6 +66,7 @@ def test_load_float_dpi() -> None:
 
 def test_load_set_dpi() -> None:
     with Image.open("Tests/images/drawing.wmf") as im:
+        assert isinstance(im, WmfImagePlugin.WmfStubImageFile)
         assert im.size == (82, 82)
 
         if hasattr(Image.core, "drawwmf"):
diff --git a/Tests/test_file_xpm.py b/Tests/test_file_xpm.py
index 26afe93f4..73c62a44d 100644
--- a/Tests/test_file_xpm.py
+++ b/Tests/test_file_xpm.py
@@ -30,6 +30,7 @@ def test_invalid_file() -> None:
 def test_load_read() -> None:
     # Arrange
     with Image.open(TEST_FILE) as im:
+        assert isinstance(im, XpmImagePlugin.XpmImageFile)
         dummy_bytes = 1
 
         # Act
diff --git a/Tests/test_image.py b/Tests/test_image.py
index 97e97acaa..f0877c5d0 100644
--- a/Tests/test_image.py
+++ b/Tests/test_image.py
@@ -605,8 +605,8 @@ class TestImage:
         assert im.mode == mode
         assert im.getpixel((0, 0)) == 0
         assert im.getpixel((255, 255)) == 255
-        with Image.open(target_file) as target:
-            target = target.convert(mode)
+        with Image.open(target_file) as img:
+            target = img.convert(mode)
         assert_image_equal(im, target)
 
     def test_radial_gradient_wrong_mode(self) -> None:
@@ -630,8 +630,8 @@ class TestImage:
         assert im.mode == mode
         assert im.getpixel((0, 0)) == 255
         assert im.getpixel((128, 128)) == 0
-        with Image.open(target_file) as target:
-            target = target.convert(mode)
+        with Image.open(target_file) as img:
+            target = img.convert(mode)
         assert_image_equal(im, target)
 
     def test_register_extensions(self) -> None:
@@ -652,8 +652,8 @@ class TestImage:
 
     def test_remap_palette(self) -> None:
         # Test identity transform
-        with Image.open("Tests/images/hopper.gif") as im:
-            assert_image_equal(im, im.remap_palette(list(range(256))))
+        with Image.open("Tests/images/hopper.gif") as img:
+            assert_image_equal(img, img.remap_palette(list(range(256))))
 
         # Test identity transform with an RGBA palette
         im = Image.new("P", (256, 1))
@@ -662,12 +662,14 @@ class TestImage:
         im.putpalette(list(range(256)) * 4, "RGBA")
         im_remapped = im.remap_palette(list(range(256)))
         assert_image_equal(im, im_remapped)
+        assert im.palette is not None
+        assert im_remapped.palette is not None
         assert im.palette.palette == im_remapped.palette.palette
 
         # Test illegal image mode
         with hopper() as im:
             with pytest.raises(ValueError):
-                im.remap_palette(None)
+                im.remap_palette([])
 
     def test_remap_palette_transparency(self) -> None:
         im = Image.new("P", (1, 2), (0, 0, 0))
@@ -768,7 +770,7 @@ class TestImage:
         assert dict(exif)
 
         # Test that exif data is cleared after another load
-        exif.load(None)
+        exif.load(b"")
         assert not dict(exif)
 
         # Test loading just the EXIF header
diff --git a/Tests/test_image_convert.py b/Tests/test_image_convert.py
index 6a925975e..3ed5784b5 100644
--- a/Tests/test_image_convert.py
+++ b/Tests/test_image_convert.py
@@ -76,8 +76,8 @@ def test_8bit() -> None:
 
 
 def test_16bit() -> None:
-    with Image.open("Tests/images/16bit.cropped.tif") as im:
-        _test_float_conversion(im)
+    with Image.open("Tests/images/16bit.cropped.tif") as img:
+        _test_float_conversion(img)
 
     for color in (65535, 65536):
         im = Image.new("I", (1, 1), color)
@@ -236,6 +236,7 @@ def test_gif_with_rgba_palette_to_p() -> None:
     with Image.open("Tests/images/hopper.gif") as im:
         im.info["transparency"] = 255
         im.load()
+        assert im.palette is not None
         assert im.palette.mode == "RGB"
         im_p = im.convert("P")
 
diff --git a/Tests/test_image_crop.py b/Tests/test_image_crop.py
index 07fec2e64..b90ce84bc 100644
--- a/Tests/test_image_crop.py
+++ b/Tests/test_image_crop.py
@@ -78,13 +78,13 @@ def test_crop_crash() -> None:
     extents = (1, 1, 10, 10)
     # works prepatch
     with Image.open(test_img) as img:
-        img2 = img.crop(extents)
-    img2.load()
+        img1 = img.crop(extents)
+    img1.load()
 
     # fail prepatch
     with Image.open(test_img) as img:
-        img = img.crop(extents)
-    img.load()
+        img2 = img.crop(extents)
+    img2.load()
 
 
 def test_crop_zero() -> None:
diff --git a/Tests/test_image_load.py b/Tests/test_image_load.py
index 4f1d63b8f..1d5f0d17c 100644
--- a/Tests/test_image_load.py
+++ b/Tests/test_image_load.py
@@ -38,6 +38,7 @@ def test_close_after_load(caplog: pytest.LogCaptureFixture) -> None:
 def test_contextmanager() -> None:
     fn = None
     with Image.open("Tests/images/hopper.gif") as im:
+        assert im.fp is not None
         fn = im.fp.fileno()
         os.fstat(fn)
 
diff --git a/Tests/test_image_putpalette.py b/Tests/test_image_putpalette.py
index f2c447f71..661764b60 100644
--- a/Tests/test_image_putpalette.py
+++ b/Tests/test_image_putpalette.py
@@ -62,6 +62,7 @@ def test_putpalette_with_alpha_values() -> None:
         expected = im.convert("RGBA")
 
         palette = im.getpalette()
+        assert palette is not None
         transparency = im.info.pop("transparency")
 
         palette_with_alpha_values = []
diff --git a/Tests/test_image_quantize.py b/Tests/test_image_quantize.py
index 7c564d967..432ec8707 100644
--- a/Tests/test_image_quantize.py
+++ b/Tests/test_image_quantize.py
@@ -56,20 +56,21 @@ def test_rgba_quantize() -> None:
 
 def test_quantize() -> None:
     with Image.open("Tests/images/caption_6_33_22.png") as image:
-        image = image.convert("RGB")
-    converted = image.quantize()
+        converted = image.convert("RGB")
+    converted = converted.quantize()
     assert converted.mode == "P"
     assert_image_similar(converted.convert("RGB"), image, 1)
 
 
 def test_quantize_no_dither() -> None:
-    image = hopper()
+    palette: Image.Image
     with Image.open("Tests/images/caption_6_33_22.png") as palette:
         palette = palette.convert("P")
 
-    converted = image.quantize(dither=Image.Dither.NONE, palette=palette)
+    converted = hopper().quantize(dither=Image.Dither.NONE, palette=palette)
     assert converted.mode == "P"
     assert converted.palette is not None
+    assert palette.palette is not None
     assert converted.palette.palette == palette.palette.palette
 
 
@@ -93,8 +94,8 @@ def test_quantize_no_dither2() -> None:
 
 def test_quantize_dither_diff() -> None:
     image = hopper()
-    with Image.open("Tests/images/caption_6_33_22.png") as palette:
-        palette = palette.convert("P")
+    with Image.open("Tests/images/caption_6_33_22.png") as im:
+        palette = im.convert("P")
 
     dither = image.quantize(dither=Image.Dither.FLOYDSTEINBERG, palette=palette)
     nodither = image.quantize(dither=Image.Dither.NONE, palette=palette)
diff --git a/Tests/test_image_resize.py b/Tests/test_image_resize.py
index c9e304512..b33e264c0 100644
--- a/Tests/test_image_resize.py
+++ b/Tests/test_image_resize.py
@@ -297,14 +297,14 @@ class TestImageResize:
         # Test unknown resampling filter
         with hopper() as im:
             with pytest.raises(ValueError):
-                im.resize((10, 10), "unknown")
+                im.resize((10, 10), -1)
 
     @skip_unless_feature("libtiff")
     def test_load_first(self) -> None:
         # load() may change the size of the image
         # Test that resize() is calling it before getting the size
-        with Image.open("Tests/images/g4_orientation_5.tif") as im:
-            im = im.resize((64, 64))
+        with Image.open("Tests/images/g4_orientation_5.tif") as img:
+            im = img.resize((64, 64))
             assert im.size == (64, 64)
 
     @pytest.mark.parametrize("mode", ("L", "RGB", "I", "F"))
diff --git a/Tests/test_image_rotate.py b/Tests/test_image_rotate.py
index 252a15db7..317328469 100644
--- a/Tests/test_image_rotate.py
+++ b/Tests/test_image_rotate.py
@@ -40,8 +40,8 @@ def test_mode(mode: str) -> None:
 
 @pytest.mark.parametrize("angle", (0, 90, 180, 270))
 def test_angle(angle: int) -> None:
-    with Image.open("Tests/images/test-card.png") as im:
-        rotate(im, im.mode, angle)
+    with Image.open("Tests/images/test-card.png") as img:
+        rotate(img, img.mode, angle)
 
     im = hopper()
     assert_image_equal(im.rotate(angle), im.rotate(angle, expand=1))
@@ -74,6 +74,7 @@ def test_center_0() -> None:
     im = hopper()
     im = im.rotate(45, center=(0, 0), resample=Image.Resampling.BICUBIC)
 
+    target: Image.Image
     with Image.open("Tests/images/hopper_45.png") as target:
         target_origin = target.size[1] / 2
         target = target.crop((0, target_origin, 128, target_origin + 128))
@@ -85,6 +86,7 @@ def test_center_14() -> None:
     im = hopper()
     im = im.rotate(45, center=(14, 14), resample=Image.Resampling.BICUBIC)
 
+    target: Image.Image
     with Image.open("Tests/images/hopper_45.png") as target:
         target_origin = target.size[1] / 2 - 14
         target = target.crop((6, target_origin, 128 + 6, target_origin + 128))
@@ -94,6 +96,8 @@ def test_center_14() -> None:
 
 def test_translate() -> None:
     im = hopper()
+
+    target: Image.Image
     with Image.open("Tests/images/hopper_45.png") as target:
         target_origin = (target.size[1] / 2 - 64) - 5
         target = target.crop(
diff --git a/Tests/test_image_thumbnail.py b/Tests/test_image_thumbnail.py
index bdbf09c40..d97232b62 100644
--- a/Tests/test_image_thumbnail.py
+++ b/Tests/test_image_thumbnail.py
@@ -106,20 +106,20 @@ def test_load_first() -> None:
         assert im.size == (590, 88)
 
 
-def test_load_first_unless_jpeg() -> None:
+def test_load_first_unless_jpeg(monkeypatch: pytest.MonkeyPatch) -> None:
     # Test that thumbnail() still uses draft() for JPEG
     with Image.open("Tests/images/hopper.jpg") as im:
-        draft = im.draft
+        orig_draft = im.draft
 
         def im_draft(
             mode: str, size: tuple[int, int]
         ) -> tuple[str, tuple[int, int, float, float]] | None:
-            result = draft(mode, size)
+            result = orig_draft(mode, size)
             assert result is not None
 
             return result
 
-        im.draft = im_draft
+        monkeypatch.setattr(im, "draft", im_draft)
 
         im.thumbnail((64, 64))
 
@@ -158,6 +158,7 @@ def test_reducing_gap_values() -> None:
 
 
 def test_reducing_gap_for_DCT_scaling() -> None:
+    ref: Image.Image
     with Image.open("Tests/images/hopper.jpg") as ref:
         # thumbnail should call draft with reducing_gap scale
         ref.draft(None, (18 * 3, 18 * 3))
diff --git a/Tests/test_image_transform.py b/Tests/test_image_transform.py
index 7e83396de..818f784b1 100644
--- a/Tests/test_image_transform.py
+++ b/Tests/test_image_transform.py
@@ -47,6 +47,8 @@ class TestImageTransform:
             transformed = im.transform(
                 im.size, Image.Transform.AFFINE, [1, 0, 0, 0, 1, 0]
             )
+            assert im.palette is not None
+            assert transformed.palette is not None
             assert im.palette.palette == transformed.palette.palette
 
     def test_extent(self) -> None:
@@ -245,14 +247,14 @@ class TestImageTransform:
     def test_missing_method_data(self) -> None:
         with hopper() as im:
             with pytest.raises(ValueError):
-                im.transform((100, 100), None)
+                im.transform((100, 100), None)  # type: ignore[arg-type]
 
     @pytest.mark.parametrize("resample", (Image.Resampling.BOX, "unknown"))
     def test_unknown_resampling_filter(self, resample: Image.Resampling | str) -> None:
         with hopper() as im:
             (w, h) = im.size
             with pytest.raises(ValueError):
-                im.transform((100, 100), Image.Transform.EXTENT, (0, 0, w, h), resample)
+                im.transform((100, 100), Image.Transform.EXTENT, (0, 0, w, h), resample)  # type: ignore[arg-type]
 
 
 class TestImageTransformAffine:
diff --git a/Tests/test_imagedraw.py b/Tests/test_imagedraw.py
index e852b8471..be5a3358e 100644
--- a/Tests/test_imagedraw.py
+++ b/Tests/test_imagedraw.py
@@ -190,6 +190,7 @@ def test_bitmap() -> None:
     # Arrange
     im = Image.new("RGB", (W, H))
     draw = ImageDraw.Draw(im)
+    small: Image.Image
     with Image.open("Tests/images/pil123rgba.png") as small:
         small = small.resize((50, 50), Image.Resampling.NEAREST)
 
diff --git a/Tests/test_imageops.py b/Tests/test_imageops.py
index 2fb2a60b6..0c5254805 100644
--- a/Tests/test_imageops.py
+++ b/Tests/test_imageops.py
@@ -249,8 +249,8 @@ def test_colorize_2color() -> None:
     # Test the colorizing function with 2-color functionality
 
     # Open test image (256px by 10px, black to white)
-    with Image.open("Tests/images/bw_gradient.png") as im:
-        im = im.convert("L")
+    with Image.open("Tests/images/bw_gradient.png") as img:
+        im = img.convert("L")
 
     # Create image with original 2-color functionality
     im_test = ImageOps.colorize(im, "red", "green")
@@ -289,8 +289,8 @@ def test_colorize_2color_offset() -> None:
     # Test the colorizing function with 2-color functionality and offset
 
     # Open test image (256px by 10px, black to white)
-    with Image.open("Tests/images/bw_gradient.png") as im:
-        im = im.convert("L")
+    with Image.open("Tests/images/bw_gradient.png") as img:
+        im = img.convert("L")
 
     # Create image with original 2-color functionality with offsets
     im_test = ImageOps.colorize(
@@ -331,8 +331,8 @@ def test_colorize_3color_offset() -> None:
     # Test the colorizing function with 3-color functionality and offset
 
     # Open test image (256px by 10px, black to white)
-    with Image.open("Tests/images/bw_gradient.png") as im:
-        im = im.convert("L")
+    with Image.open("Tests/images/bw_gradient.png") as img:
+        im = img.convert("L")
 
     # Create image with new three color functionality with offsets
     im_test = ImageOps.colorize(
@@ -428,6 +428,7 @@ def test_exif_transpose() -> None:
                     check(orientation_im)
 
     # Orientation from "XML:com.adobe.xmp" info key
+    im: Image.Image
     for suffix in ("", "_exiftool"):
         with Image.open("Tests/images/xmp_tags_orientation" + suffix + ".png") as im:
             assert im.getexif()[0x0112] == 3
@@ -442,10 +443,10 @@ def test_exif_transpose() -> None:
     # Orientation from "Raw profile type exif" info key
     # This test image has been manually hexedited from exif_imagemagick.png
     # to have a different orientation
-    with Image.open("Tests/images/exif_imagemagick_orientation.png") as im:
-        assert im.getexif()[0x0112] == 3
+    with Image.open("Tests/images/exif_imagemagick_orientation.png") as img:
+        assert img.getexif()[0x0112] == 3
 
-        transposed_im = ImageOps.exif_transpose(im)
+        transposed_im = ImageOps.exif_transpose(img)
         assert transposed_im is not None
         assert 0x0112 not in transposed_im.getexif()
 
diff --git a/Tests/test_imagepalette.py b/Tests/test_imagepalette.py
index 6cf0079dd..e2f8308ea 100644
--- a/Tests/test_imagepalette.py
+++ b/Tests/test_imagepalette.py
@@ -17,6 +17,7 @@ def test_sanity() -> None:
 def test_reload() -> None:
     with Image.open("Tests/images/hopper.gif") as im:
         original = im.copy()
+        assert im.palette is not None
         im.palette.dirty = 1
         assert_image_equal(im.convert("RGB"), original.convert("RGB"))
 
diff --git a/Tests/test_imagesequence.py b/Tests/test_imagesequence.py
index 9b37435eb..ff55073f5 100644
--- a/Tests/test_imagesequence.py
+++ b/Tests/test_imagesequence.py
@@ -4,7 +4,7 @@ from pathlib import Path
 
 import pytest
 
-from PIL import Image, ImageSequence, TiffImagePlugin
+from PIL import Image, ImageSequence, PsdImagePlugin, TiffImagePlugin
 
 from .helper import assert_image_equal, hopper, skip_unless_feature
 
@@ -31,6 +31,8 @@ def test_sanity(tmp_path: Path) -> None:
 
 def test_iterator() -> None:
     with Image.open("Tests/images/multipage.tiff") as im:
+        assert isinstance(im, TiffImagePlugin.TiffImageFile)
+
         i = ImageSequence.Iterator(im)
         for index in range(0, im.n_frames):
             assert i[index] == next(i)
@@ -42,6 +44,8 @@ def test_iterator() -> None:
 
 def test_iterator_min_frame() -> None:
     with Image.open("Tests/images/hopper.psd") as im:
+        assert isinstance(im, PsdImagePlugin.PsdImageFile)
+
         i = ImageSequence.Iterator(im)
         for index in range(1, im.n_frames):
             assert i[index] == next(i)
@@ -74,9 +78,14 @@ def test_consecutive() -> None:
 def test_palette_mmap() -> None:
     # Using mmap in ImageFile can require to reload the palette.
     with Image.open("Tests/images/multipage-mmap.tiff") as im:
-        color1 = im.getpalette()[:3]
+        palette = im.getpalette()
+        assert palette is not None
+        color1 = palette[:3]
         im.seek(0)
-        color2 = im.getpalette()[:3]
+
+        palette = im.getpalette()
+        assert palette is not None
+        color2 = palette[:3]
         assert color1 == color2
 
 
diff --git a/Tests/test_pickle.py b/Tests/test_pickle.py
index be143e9c6..15760b465 100644
--- a/Tests/test_pickle.py
+++ b/Tests/test_pickle.py
@@ -17,6 +17,7 @@ def helper_pickle_file(
     tmp_path: Path, protocol: int, test_file: str, mode: str | None
 ) -> None:
     # Arrange
+    im: Image.Image
     with Image.open(test_file) as im:
         filename = str(tmp_path / "temp.pkl")
         if mode:
@@ -33,6 +34,7 @@ def helper_pickle_file(
 
 
 def helper_pickle_string(protocol: int, test_file: str, mode: str | None) -> None:
+    im: Image.Image
     with Image.open(test_file) as im:
         if mode:
             im = im.convert(mode)
@@ -77,8 +79,8 @@ def test_pickle_image(
 def test_pickle_la_mode_with_palette(tmp_path: Path) -> None:
     # Arrange
     filename = str(tmp_path / "temp.pkl")
-    with Image.open("Tests/images/hopper.jpg") as im:
-        im = im.convert("PA")
+    with Image.open("Tests/images/hopper.jpg") as img:
+        im = img.convert("PA")
 
     # Act / Assert
     for protocol in range(0, pickle.HIGHEST_PROTOCOL + 1):
diff --git a/Tests/test_shell_injection.py b/Tests/test_shell_injection.py
index dd4fc46c3..508d89352 100644
--- a/Tests/test_shell_injection.py
+++ b/Tests/test_shell_injection.py
@@ -39,6 +39,7 @@ class TestShellInjection:
             shutil.copy(TEST_JPG, src_file)
 
             with Image.open(src_file) as im:
+                assert isinstance(im, JpegImagePlugin.JpegImageFile)
                 im.load_djpeg()
 
     @pytest.mark.skipif(not cjpeg_available(), reason="cjpeg not available")
@@ -49,11 +50,13 @@ class TestShellInjection:
     @pytest.mark.skipif(not netpbm_available(), reason="Netpbm not available")
     def test_save_netpbm_filename_bmp_mode(self, tmp_path: Path) -> None:
         with Image.open(TEST_GIF) as im:
-            im = im.convert("RGB")
-            self.assert_save_filename_check(tmp_path, im, GifImagePlugin._save_netpbm)
+            im_rgb = im.convert("RGB")
+            self.assert_save_filename_check(
+                tmp_path, im_rgb, GifImagePlugin._save_netpbm
+            )
 
     @pytest.mark.skipif(not netpbm_available(), reason="Netpbm not available")
     def test_save_netpbm_filename_l_mode(self, tmp_path: Path) -> None:
         with Image.open(TEST_GIF) as im:
-            im = im.convert("L")
-            self.assert_save_filename_check(tmp_path, im, GifImagePlugin._save_netpbm)
+            im_l = im.convert("L")
+            self.assert_save_filename_check(tmp_path, im_l, GifImagePlugin._save_netpbm)
diff --git a/Tests/test_tiff_ifdrational.py b/Tests/test_tiff_ifdrational.py
index 13f1f9c80..6df1e4557 100644
--- a/Tests/test_tiff_ifdrational.py
+++ b/Tests/test_tiff_ifdrational.py
@@ -72,4 +72,5 @@ def test_ifd_rational_save(
     im.save(out, dpi=(res, res), compression="raw")
 
     with Image.open(out) as reloaded:
+        assert isinstance(reloaded, TiffImagePlugin.TiffImageFile)
         assert float(IFDRational(301, 1)) == float(reloaded.tag_v2[282])
diff --git a/docs/example/DdsImagePlugin.py b/docs/example/DdsImagePlugin.py
index 10828bff0..b464ae58d 100644
--- a/docs/example/DdsImagePlugin.py
+++ b/docs/example/DdsImagePlugin.py
@@ -213,6 +213,7 @@ class DdsImageFile(ImageFile.ImageFile):
     format_description = "DirectDraw Surface"
 
     def _open(self) -> None:
+        assert self.fp is not None
         if not _accept(self.fp.read(4)):
             msg = "not a DDS file"
             raise SyntaxError(msg)
diff --git a/src/PIL/BlpImagePlugin.py b/src/PIL/BlpImagePlugin.py
index e5605635e..aa9ba9e27 100644
--- a/src/PIL/BlpImagePlugin.py
+++ b/src/PIL/BlpImagePlugin.py
@@ -258,6 +258,7 @@ class BlpImageFile(ImageFile.ImageFile):
     format_description = "Blizzard Mipmap Format"
 
     def _open(self) -> None:
+        assert self.fp is not None
         self.magic = self.fp.read(4)
 
         self.fp.seek(5, os.SEEK_CUR)
diff --git a/src/PIL/BmpImagePlugin.py b/src/PIL/BmpImagePlugin.py
index bf8f29577..45b608d85 100644
--- a/src/PIL/BmpImagePlugin.py
+++ b/src/PIL/BmpImagePlugin.py
@@ -74,6 +74,7 @@ class BmpImageFile(ImageFile.ImageFile):
 
     def _bitmap(self, header: int = 0, offset: int = 0) -> None:
         """Read relevant info about the BMP"""
+        assert self.fp is not None
         read, seek = self.fp.read, self.fp.seek
         if header:
             seek(header)
@@ -307,6 +308,7 @@ class BmpImageFile(ImageFile.ImageFile):
     def _open(self) -> None:
         """Open file, check magic number and read header"""
         # read 14 bytes: magic number, filesize, reserved, header final offset
+        assert self.fp is not None
         head_data = self.fp.read(14)
         # choke if the file does not have the required magic bytes
         if not _accept(head_data):
diff --git a/src/PIL/BufrStubImagePlugin.py b/src/PIL/BufrStubImagePlugin.py
index 0ee2f653b..521e5defd 100644
--- a/src/PIL/BufrStubImagePlugin.py
+++ b/src/PIL/BufrStubImagePlugin.py
@@ -40,6 +40,7 @@ class BufrStubImageFile(ImageFile.StubImageFile):
     format_description = "BUFR"
 
     def _open(self) -> None:
+        assert self.fp is not None
         offset = self.fp.tell()
 
         if not _accept(self.fp.read(4)):
diff --git a/src/PIL/CurImagePlugin.py b/src/PIL/CurImagePlugin.py
index c4be0ceca..4688a30f7 100644
--- a/src/PIL/CurImagePlugin.py
+++ b/src/PIL/CurImagePlugin.py
@@ -38,6 +38,7 @@ class CurImageFile(BmpImagePlugin.BmpImageFile):
     format_description = "Windows Cursor"
 
     def _open(self) -> None:
+        assert self.fp is not None
         offset = self.fp.tell()
 
         # check magic
diff --git a/src/PIL/DcxImagePlugin.py b/src/PIL/DcxImagePlugin.py
index f67f27d73..d3f456ddc 100644
--- a/src/PIL/DcxImagePlugin.py
+++ b/src/PIL/DcxImagePlugin.py
@@ -24,6 +24,7 @@ from __future__ import annotations
 
 from . import Image
 from ._binary import i32le as i32
+from ._util import DeferredError
 from .PcxImagePlugin import PcxImageFile
 
 MAGIC = 0x3ADE68B1  # QUIZ: what's this value, then?
@@ -44,6 +45,7 @@ class DcxImageFile(PcxImageFile):
 
     def _open(self) -> None:
         # Header
+        assert self.fp is not None
         s = self.fp.read(4)
         if not _accept(s):
             msg = "not a DCX file"
@@ -66,6 +68,8 @@ class DcxImageFile(PcxImageFile):
     def seek(self, frame: int) -> None:
         if not self._seek_check(frame):
             return
+        if isinstance(self._fp, DeferredError):
+            raise self._fp.ex
         self.frame = frame
         self.fp = self._fp
         self.fp.seek(self._offset[frame])
diff --git a/src/PIL/DdsImagePlugin.py b/src/PIL/DdsImagePlugin.py
index 1b6408237..540d12ad6 100644
--- a/src/PIL/DdsImagePlugin.py
+++ b/src/PIL/DdsImagePlugin.py
@@ -333,6 +333,7 @@ class DdsImageFile(ImageFile.ImageFile):
     format_description = "DirectDraw Surface"
 
     def _open(self) -> None:
+        assert self.fp is not None
         if not _accept(self.fp.read(4)):
             msg = "not a DDS file"
             raise SyntaxError(msg)
diff --git a/src/PIL/EpsImagePlugin.py b/src/PIL/EpsImagePlugin.py
index dd6ae4a77..f71e7e151 100644
--- a/src/PIL/EpsImagePlugin.py
+++ b/src/PIL/EpsImagePlugin.py
@@ -184,6 +184,7 @@ class EpsImageFile(ImageFile.ImageFile):
     mode_map = {1: "L", 2: "LAB", 3: "RGB", 4: "CMYK"}
 
     def _open(self) -> None:
+        assert self.fp is not None
         (length, offset) = self._find_offset(self.fp)
 
         # go to offset - start of "%!PS"
@@ -377,6 +378,7 @@ class EpsImageFile(ImageFile.ImageFile):
     ) -> Image.core.PixelAccess | None:
         # Load EPS via Ghostscript
         if self.tile:
+            assert self.fp is not None
             self.im = Ghostscript(self.tile, self.size, self.fp, scale, transparency)
             self._mode = self.im.mode
             self._size = self.im.size
diff --git a/src/PIL/FliImagePlugin.py b/src/PIL/FliImagePlugin.py
index 666390be9..f46232963 100644
--- a/src/PIL/FliImagePlugin.py
+++ b/src/PIL/FliImagePlugin.py
@@ -22,6 +22,7 @@ from . import Image, ImageFile, ImagePalette
 from ._binary import i16le as i16
 from ._binary import i32le as i32
 from ._binary import o8
+from ._util import DeferredError
 
 #
 # decoder
@@ -47,6 +48,7 @@ class FliImageFile(ImageFile.ImageFile):
 
     def _open(self) -> None:
         # HEAD
+        assert self.fp is not None
         s = self.fp.read(128)
         if not (_accept(s) and s[20:22] == b"\x00\x00"):
             msg = "not an FLI/FLC file"
@@ -110,6 +112,7 @@ class FliImageFile(ImageFile.ImageFile):
         # load palette
 
         i = 0
+        assert self.fp is not None
         for e in range(i16(self.fp.read(2))):
             s = self.fp.read(2)
             i = i + s[0]
@@ -134,6 +137,8 @@ class FliImageFile(ImageFile.ImageFile):
             self._seek(f)
 
     def _seek(self, frame: int) -> None:
+        if isinstance(self._fp, DeferredError):
+            raise self._fp.ex
         if frame == 0:
             self.__frame = -1
             self._fp.seek(self.__rewind)
diff --git a/src/PIL/FpxImagePlugin.py b/src/PIL/FpxImagePlugin.py
index 8fef51076..d650be026 100644
--- a/src/PIL/FpxImagePlugin.py
+++ b/src/PIL/FpxImagePlugin.py
@@ -58,6 +58,7 @@ class FpxImageFile(ImageFile.ImageFile):
         # read the OLE directory and see if this is a likely
         # to be a FlashPix file
 
+        assert self.fp is not None
         try:
             self.ole = olefile.OleFileIO(self.fp)
         except OSError as e:
@@ -229,6 +230,7 @@ class FpxImageFile(ImageFile.ImageFile):
                 if y >= ysize:
                     break  # isn't really required
 
+        assert self.fp is not None
         self.stream = stream
         self._fp = self.fp
         self.fp = None
diff --git a/src/PIL/FtexImagePlugin.py b/src/PIL/FtexImagePlugin.py
index ddb469bc3..a875a097f 100644
--- a/src/PIL/FtexImagePlugin.py
+++ b/src/PIL/FtexImagePlugin.py
@@ -72,6 +72,7 @@ class FtexImageFile(ImageFile.ImageFile):
     format_description = "Texture File Format (IW2:EOC)"
 
     def _open(self) -> None:
+        assert self.fp is not None
         if not _accept(self.fp.read(4)):
             msg = "not an FTEX file"
             raise SyntaxError(msg)
diff --git a/src/PIL/GbrImagePlugin.py b/src/PIL/GbrImagePlugin.py
index f319d7e84..a61bb883f 100644
--- a/src/PIL/GbrImagePlugin.py
+++ b/src/PIL/GbrImagePlugin.py
@@ -42,6 +42,7 @@ class GbrImageFile(ImageFile.ImageFile):
     format_description = "GIMP brush file"
 
     def _open(self) -> None:
+        assert self.fp is not None
         header_size = i32(self.fp.read(4))
         if header_size < 20:
             msg = "not a GIMP brush"
@@ -91,6 +92,8 @@ class GbrImageFile(ImageFile.ImageFile):
     def load(self) -> Image.core.PixelAccess | None:
         if self._im is None:
             self.im = Image.core.new(self.mode, self.size)
+
+            assert self.fp is not None
             self.frombytes(self.fp.read(self._data_size))
         return Image.Image.load(self)
 
diff --git a/src/PIL/GifImagePlugin.py b/src/PIL/GifImagePlugin.py
index f206fbb9c..0d96f457c 100644
--- a/src/PIL/GifImagePlugin.py
+++ b/src/PIL/GifImagePlugin.py
@@ -31,7 +31,7 @@ import os
 import subprocess
 from enum import IntEnum
 from functools import cached_property
-from typing import IO, TYPE_CHECKING, Any, Literal, NamedTuple, Union
+from typing import IO, TYPE_CHECKING, Any, Literal, NamedTuple, Union, cast
 
 from . import (
     Image,
@@ -45,6 +45,7 @@ from . import (
 from ._binary import i16le as i16
 from ._binary import o8
 from ._binary import o16le as o16
+from ._util import DeferredError
 
 if TYPE_CHECKING:
     from . import _imaging
@@ -83,6 +84,7 @@ class GifImageFile(ImageFile.ImageFile):
     global_palette = None
 
     def data(self) -> bytes | None:
+        assert self.fp is not None
         s = self.fp.read(1)
         if s and s[0]:
             return self.fp.read(s[0])
@@ -96,6 +98,7 @@ class GifImageFile(ImageFile.ImageFile):
 
     def _open(self) -> None:
         # Screen
+        assert self.fp is not None
         s = self.fp.read(13)
         if not _accept(s):
             msg = "not a GIF file"
@@ -113,8 +116,8 @@ class GifImageFile(ImageFile.ImageFile):
             # check if palette contains colour indices
             p = self.fp.read(3 << bits)
             if self._is_palette_needed(p):
-                p = ImagePalette.raw("RGB", p)
-                self.global_palette = self.palette = p
+                palette = ImagePalette.raw("RGB", p)
+                self.global_palette = self.palette = palette
 
         self._fp = self.fp  # FIXME: hack
         self.__rewind = self.fp.tell()
@@ -168,6 +171,8 @@ class GifImageFile(ImageFile.ImageFile):
                 raise EOFError(msg) from e
 
     def _seek(self, frame: int, update_image: bool = True) -> None:
+        if isinstance(self._fp, DeferredError):
+            raise self._fp.ex
         if frame == 0:
             # rewind
             self.__offset = 0
@@ -251,7 +256,7 @@ class GifImageFile(ImageFile.ImageFile):
                         info["comment"] += b"\n" + comment
                     else:
                         info["comment"] = comment
-                    s = None
+                    s = b""
                     continue
                 elif s[0] == 255 and frame == 0 and block is not None:
                     #
@@ -294,7 +299,7 @@ class GifImageFile(ImageFile.ImageFile):
                 bits = self.fp.read(1)[0]
                 self.__offset = self.fp.tell()
                 break
-            s = None
+            s = b""
 
         if interlace is None:
             msg = "image not found in GIF frame"
@@ -347,7 +352,10 @@ class GifImageFile(ImageFile.ImageFile):
             if self._frame_palette:
                 if color * 3 + 3 > len(self._frame_palette.palette):
                     color = 0
-                return tuple(self._frame_palette.palette[color * 3 : color * 3 + 3])
+                return cast(
+                    tuple[int, int, int],
+                    tuple(self._frame_palette.palette[color * 3 : color * 3 + 3]),
+                )
             else:
                 return (color, color, color)
 
diff --git a/src/PIL/GribStubImagePlugin.py b/src/PIL/GribStubImagePlugin.py
index e9aa084b2..63ec390ae 100644
--- a/src/PIL/GribStubImagePlugin.py
+++ b/src/PIL/GribStubImagePlugin.py
@@ -40,6 +40,7 @@ class GribStubImageFile(ImageFile.StubImageFile):
     format_description = "GRIB"
 
     def _open(self) -> None:
+        assert self.fp is not None
         offset = self.fp.tell()
 
         if not _accept(self.fp.read(8)):
diff --git a/src/PIL/Hdf5StubImagePlugin.py b/src/PIL/Hdf5StubImagePlugin.py
index cc9e73deb..b3e73064f 100644
--- a/src/PIL/Hdf5StubImagePlugin.py
+++ b/src/PIL/Hdf5StubImagePlugin.py
@@ -40,6 +40,7 @@ class HDF5StubImageFile(ImageFile.StubImageFile):
     format_description = "HDF5"
 
     def _open(self) -> None:
+        assert self.fp is not None
         offset = self.fp.tell()
 
         if not _accept(self.fp.read(8)):
diff --git a/src/PIL/IcnsImagePlugin.py b/src/PIL/IcnsImagePlugin.py
index ca66aa0fd..faf02779a 100644
--- a/src/PIL/IcnsImagePlugin.py
+++ b/src/PIL/IcnsImagePlugin.py
@@ -266,6 +266,7 @@ class IcnsImageFile(ImageFile.ImageFile):
     format_description = "Mac OS icns resource"
 
     def _open(self) -> None:
+        assert self.fp is not None
         self.icns = IcnsFile(self.fp)
         self._mode = "RGBA"
         self.info["sizes"] = self.icns.itersizes()
diff --git a/src/PIL/IcoImagePlugin.py b/src/PIL/IcoImagePlugin.py
index e879f1801..2eb12f86a 100644
--- a/src/PIL/IcoImagePlugin.py
+++ b/src/PIL/IcoImagePlugin.py
@@ -326,6 +326,7 @@ class IcoImageFile(ImageFile.ImageFile):
     format_description = "Windows Icon"
 
     def _open(self) -> None:
+        assert self.fp is not None
         self.ico = IcoFile(self.fp)
         self.info["sizes"] = self.ico.sizes()
         self.size = self.ico.entry[0].dim
diff --git a/src/PIL/ImImagePlugin.py b/src/PIL/ImImagePlugin.py
index f9f47348c..a12a45866 100644
--- a/src/PIL/ImImagePlugin.py
+++ b/src/PIL/ImImagePlugin.py
@@ -31,6 +31,7 @@ import re
 from typing import IO, Any
 
 from . import Image, ImageFile, ImagePalette
+from ._util import DeferredError
 
 # --------------------------------------------------------------------
 # Standard tags
@@ -124,6 +125,7 @@ class ImImageFile(ImageFile.ImageFile):
         # Quick rejection: if there's not an LF among the first
         # 100 bytes, this is (probably) not a text header.
 
+        assert self.fp is not None
         if b"\n" not in self.fp.read(100):
             msg = "not an IM file"
             raise SyntaxError(msg)
@@ -301,6 +303,8 @@ class ImImageFile(ImageFile.ImageFile):
         size = ((self.size[0] * bits + 7) // 8) * self.size[1]
         offs = self.__offset + frame * size
 
+        if isinstance(self._fp, DeferredError):
+            raise self._fp.ex
         self.fp = self._fp
 
         self.tile = [
diff --git a/src/PIL/Image.py b/src/PIL/Image.py
index e6d9047f5..a1216cf17 100644
--- a/src/PIL/Image.py
+++ b/src/PIL/Image.py
@@ -604,22 +604,11 @@ class Image:
         return new
 
     # Context manager support
-    def __enter__(self):
+    def __enter__(self) -> Image:
         return self
 
-    def _close_fp(self):
-        if getattr(self, "_fp", False):
-            if self._fp != self.fp:
-                self._fp.close()
-            self._fp = DeferredError(ValueError("Operation on closed image"))
-        if self.fp:
-            self.fp.close()
-
-    def __exit__(self, *args):
-        if hasattr(self, "fp"):
-            if getattr(self, "_exclusive_fp", False):
-                self._close_fp()
-            self.fp = None
+    def __exit__(self, *args: object) -> None:
+        pass
 
     def close(self) -> None:
         """
@@ -633,13 +622,6 @@ class Image:
         :py:meth:`~PIL.Image.Image.load` method. See :ref:`file-handling` for
         more information.
         """
-        if hasattr(self, "fp"):
-            try:
-                self._close_fp()
-                self.fp = None
-            except Exception as msg:
-                logger.debug("Error closing: %s", msg)
-
         if getattr(self, "map", None):
             self.map: mmap.mmap | None = None
 
@@ -1543,10 +1525,14 @@ class Image:
                 exif_info = bytes.fromhex(
                     "".join(self.info["Raw profile type exif"].split("\n")[3:])
                 )
-            elif hasattr(self, "tag_v2"):
-                self._exif.bigtiff = self.tag_v2._bigtiff
-                self._exif.endian = self.tag_v2._endian
-                self._exif.load_from_fp(self.fp, self.tag_v2._offset)
+            else:
+                from . import TiffImagePlugin
+
+                if isinstance(self, TiffImagePlugin.TiffImageFile):
+                    self._exif.bigtiff = self.tag_v2._bigtiff
+                    self._exif.endian = self.tag_v2._endian
+                    assert self.fp is not None
+                    self._exif.load_from_fp(self.fp, self.tag_v2._offset)
         if exif_info is not None:
             self._exif.load(exif_info)
 
@@ -1566,52 +1552,6 @@ class Image:
         self._exif._loaded = False
         self.getexif()
 
-    def get_child_images(self) -> list[ImageFile.ImageFile]:
-        child_images = []
-        exif = self.getexif()
-        ifds = []
-        if ExifTags.Base.SubIFDs in exif:
-            subifd_offsets = exif[ExifTags.Base.SubIFDs]
-            if subifd_offsets:
-                if not isinstance(subifd_offsets, tuple):
-                    subifd_offsets = (subifd_offsets,)
-                for subifd_offset in subifd_offsets:
-                    ifds.append((exif._get_ifd_dict(subifd_offset), subifd_offset))
-        ifd1 = exif.get_ifd(ExifTags.IFD.IFD1)
-        if ifd1 and ifd1.get(513):
-            assert exif._info is not None
-            ifds.append((ifd1, exif._info.next))
-
-        offset = None
-        for ifd, ifd_offset in ifds:
-            current_offset = self.fp.tell()
-            if offset is None:
-                offset = current_offset
-
-            fp = self.fp
-            if ifd is not None:
-                thumbnail_offset = ifd.get(513)
-                if thumbnail_offset is not None:
-                    thumbnail_offset += getattr(self, "_exif_offset", 0)
-                    self.fp.seek(thumbnail_offset)
-                    data = self.fp.read(ifd.get(514))
-                    fp = io.BytesIO(data)
-
-            with open(fp) as im:
-                from . import TiffImagePlugin
-
-                if thumbnail_offset is None and isinstance(
-                    im, TiffImagePlugin.TiffImageFile
-                ):
-                    im._frame_pos = [ifd_offset]
-                    im._seek(0)
-                im.load()
-                child_images.append(im)
-
-        if offset is not None:
-            self.fp.seek(offset)
-        return child_images
-
     def getim(self) -> CapsuleType:
         """
         Returns a capsule that points to the internal image memory.
@@ -2522,7 +2462,10 @@ class Image:
         )
 
     def save(
-        self, fp: StrOrBytesPath | IO[bytes], format: str | None = None, **params: Any
+        self,
+        fp: StrOrBytesPath | IO[bytes] | io.TextIOWrapper,
+        format: str | None = None,
+        **params: Any,
     ) -> None:
         """
         Saves this image under the given filename.  If no format is
diff --git a/src/PIL/ImageFile.py b/src/PIL/ImageFile.py
index b8bf0b7fe..6fdc9c7cb 100644
--- a/src/PIL/ImageFile.py
+++ b/src/PIL/ImageFile.py
@@ -31,18 +31,21 @@ from __future__ import annotations
 import abc
 import io
 import itertools
+import logging
 import os
 import struct
 import sys
 from typing import IO, TYPE_CHECKING, Any, NamedTuple, cast
 
-from . import Image
+from . import ExifTags, Image
 from ._deprecate import deprecate
-from ._util import is_path
+from ._util import DeferredError, is_path
 
 if TYPE_CHECKING:
     from ._typing import StrOrBytesPath
 
+logger = logging.getLogger(__name__)
+
 MAXBLOCK = 65536
 
 SAFEBLOCK = 1024 * 1024
@@ -127,6 +130,8 @@ class ImageFile(Image.Image):
         self.decoderconfig: tuple[Any, ...] = ()
         self.decodermaxblock = MAXBLOCK
 
+        self.fp: IO[bytes] | None
+        self._fp: IO[bytes] | DeferredError
         if is_path(fp):
             # filename
             self.fp = open(fp, "rb")
@@ -163,6 +168,93 @@ class ImageFile(Image.Image):
     def _open(self) -> None:
         pass
 
+    # Context manager support
+    def __enter__(self) -> ImageFile:
+        return self
+
+    def _close_fp(self) -> None:
+        if getattr(self, "_fp", False):
+            if self._fp != self.fp and not isinstance(self._fp, DeferredError):
+                self._fp.close()
+            self._fp = DeferredError(ValueError("Operation on closed image"))
+        if self.fp:
+            self.fp.close()
+
+    def __exit__(self, *args: object) -> None:
+        if getattr(self, "_exclusive_fp", False):
+            self._close_fp()
+        self.fp = None
+
+    def close(self) -> None:
+        """
+        Closes the file pointer, if possible.
+
+        This operation will destroy the image core and release its memory.
+        The image data will be unusable afterward.
+
+        This function is required to close images that have multiple frames or
+        have not had their file read and closed by the
+        :py:meth:`~PIL.Image.Image.load` method. See :ref:`file-handling` for
+        more information.
+        """
+        try:
+            self._close_fp()
+            self.fp = None
+        except Exception as msg:
+            logger.debug("Error closing: %s", msg)
+
+        super().close()
+
+    def get_child_images(self) -> list[ImageFile]:
+        child_images = []
+        exif = self.getexif()
+        ifds = []
+        if ExifTags.Base.SubIFDs in exif:
+            subifd_offsets = exif[ExifTags.Base.SubIFDs]
+            if subifd_offsets:
+                if not isinstance(subifd_offsets, tuple):
+                    subifd_offsets = (subifd_offsets,)
+                for subifd_offset in subifd_offsets:
+                    ifds.append((exif._get_ifd_dict(subifd_offset), subifd_offset))
+        ifd1 = exif.get_ifd(ExifTags.IFD.IFD1)
+        if ifd1 and ifd1.get(513):
+            assert exif._info is not None
+            ifds.append((ifd1, exif._info.next))
+
+        offset = None
+        assert self.fp is not None
+        for ifd, ifd_offset in ifds:
+            current_offset = self.fp.tell()
+            if offset is None:
+                offset = current_offset
+
+            fp = self.fp
+            if ifd is not None:
+                thumbnail_offset = ifd.get(513)
+                if thumbnail_offset is not None:
+                    thumbnail_offset += getattr(self, "_exif_offset", 0)
+                    self.fp.seek(thumbnail_offset)
+
+                    length = ifd.get(514)
+                    assert isinstance(length, int)
+                    data = self.fp.read(length)
+                    fp = io.BytesIO(data)
+
+            with Image.open(fp) as im:
+                from . import TiffImagePlugin
+
+                if thumbnail_offset is None and isinstance(
+                    im, TiffImagePlugin.TiffImageFile
+                ):
+                    im._frame_pos = [ifd_offset]
+                    im._seek(0)
+                im.load()
+                child_images.append(im)
+
+        if offset is not None:
+            self.fp.seek(offset)
+        return child_images
+
     def get_format_mimetype(self) -> str | None:
         if self.custom_mimetype:
             return self.custom_mimetype
@@ -179,7 +271,7 @@ class ImageFile(Image.Image):
 
         # raise exception if something's wrong.  must be called
         # directly after open, and closes file when finished.
-        if self._exclusive_fp:
+        if self._exclusive_fp and self.fp:
             self.fp.close()
         self.fp = None
 
@@ -199,6 +291,7 @@ class ImageFile(Image.Image):
         # As of pypy 2.1.0, memory mapping was failing here.
         use_mmap = use_mmap and not hasattr(sys, "pypy_version_info")
 
+        assert self.fp is not None
         readonly = 0
 
         # look for read/seek overrides
diff --git a/src/PIL/IptcImagePlugin.py b/src/PIL/IptcImagePlugin.py
index 60ab7c83f..7ca5e6680 100644
--- a/src/PIL/IptcImagePlugin.py
+++ b/src/PIL/IptcImagePlugin.py
@@ -77,6 +77,7 @@ class IptcImageFile(ImageFile.ImageFile):
     def field(self) -> tuple[tuple[int, int] | None, int]:
         #
         # get a IPTC field header
+        assert self.fp is not None
         s = self.fp.read(5)
         if not s.strip(b"\x00"):
             return None, 0
@@ -104,6 +105,7 @@ class IptcImageFile(ImageFile.ImageFile):
 
     def _open(self) -> None:
         # load descriptive fields
+        assert self.fp is not None
         while True:
             offset = self.fp.tell()
             tag, size = self.field()
@@ -157,6 +159,7 @@ class IptcImageFile(ImageFile.ImageFile):
 
         offset, compression = self.tile[0][2:]
 
+        assert self.fp is not None
         self.fp.seek(offset)
 
         # Copy image data to temporary file
@@ -165,6 +168,7 @@ class IptcImageFile(ImageFile.ImageFile):
             # To simplify access to the extracted file,
             # prepend a PPM header
             o.write(b"P5\n%d %d\n255\n" % self.size)
+        assert self.fp is not None
         while True:
             type, size = self.field()
             if type != (8, 10):
@@ -188,7 +192,7 @@ Image.register_extension(IptcImageFile.format, ".iim")
 
 
 def getiptcinfo(
-    im: ImageFile.ImageFile,
+    im: Image.Image,
 ) -> dict[tuple[int, int], bytes | list[bytes]] | None:
     """
     Get IPTC information from TIFF, JPEG, or IPTC file.
diff --git a/src/PIL/Jpeg2KImagePlugin.py b/src/PIL/Jpeg2KImagePlugin.py
index b6ebd562b..f4bb9c445 100644
--- a/src/PIL/Jpeg2KImagePlugin.py
+++ b/src/PIL/Jpeg2KImagePlugin.py
@@ -248,6 +248,7 @@ class Jpeg2KImageFile(ImageFile.ImageFile):
     format_description = "JPEG 2000 (ISO 15444)"
 
     def _open(self) -> None:
+        assert self.fp is not None
         sig = self.fp.read(4)
         if sig == b"\xff\x4f\xff\x51":
             self.codec = "j2k"
@@ -296,6 +297,7 @@ class Jpeg2KImageFile(ImageFile.ImageFile):
         ]
 
     def _parse_comment(self) -> None:
+        assert self.fp is not None
         hdr = self.fp.read(2)
         length = _binary.i16be(hdr)
         self.fp.seek(length - 2, os.SEEK_CUR)
diff --git a/src/PIL/JpegImagePlugin.py b/src/PIL/JpegImagePlugin.py
index 6510e072e..bfc922e21 100644
--- a/src/PIL/JpegImagePlugin.py
+++ b/src/PIL/JpegImagePlugin.py
@@ -60,6 +60,7 @@ if TYPE_CHECKING:
 
 
 def Skip(self: JpegImageFile, marker: int) -> None:
+    assert self.fp is not None
     n = i16(self.fp.read(2)) - 2
     ImageFile._safe_read(self.fp, n)
 
@@ -69,6 +70,7 @@ def APP(self: JpegImageFile, marker: int) -> None:
     # Application marker.  Store these in the APP dictionary.
     # Also look for well-known application markers.
 
+    assert self.fp is not None
     n = i16(self.fp.read(2)) - 2
     s = ImageFile._safe_read(self.fp, n)
 
@@ -170,6 +172,7 @@ def APP(self: JpegImageFile, marker: int) -> None:
 def COM(self: JpegImageFile, marker: int) -> None:
     #
     # Comment marker.  Store these in the APP dictionary.
+    assert self.fp is not None
     n = i16(self.fp.read(2)) - 2
     s = ImageFile._safe_read(self.fp, n)
 
@@ -186,6 +189,7 @@ def SOF(self: JpegImageFile, marker: int) -> None:
     # mode.  Note that this could be made a bit brighter, by
     # looking for JFIF and Adobe APP markers.
 
+    assert self.fp is not None
     n = i16(self.fp.read(2)) - 2
     s = ImageFile._safe_read(self.fp, n)
     self._size = i16(s, 3), i16(s, 1)
@@ -234,6 +238,7 @@ def DQT(self: JpegImageFile, marker: int) -> None:
     # FIXME: The quantization tables can be used to estimate the
     # compression quality.
 
+    assert self.fp is not None
     n = i16(self.fp.read(2)) - 2
     s = ImageFile._safe_read(self.fp, n)
     while len(s):
@@ -334,6 +339,7 @@ class JpegImageFile(ImageFile.ImageFile):
     format_description = "JPEG (ISO 10918)"
 
     def _open(self) -> None:
+        assert self.fp is not None
         s = self.fp.read(3)
 
         if not _accept(s):
@@ -401,6 +407,7 @@ class JpegImageFile(ImageFile.ImageFile):
         For premature EOF and LOAD_TRUNCATED_IMAGES adds EOI marker
         so libjpeg can finish decoding
         """
+        assert self.fp is not None
         s = self.fp.read(read_bytes)
 
         if not s and ImageFile.LOAD_TRUNCATED_IMAGES and not hasattr(self, "_ended"):
diff --git a/src/PIL/MicImagePlugin.py b/src/PIL/MicImagePlugin.py
index 5f23a34b9..ba5daaafc 100644
--- a/src/PIL/MicImagePlugin.py
+++ b/src/PIL/MicImagePlugin.py
@@ -67,6 +67,7 @@ class MicImageFile(TiffImagePlugin.TiffImageFile):
         self._n_frames = len(self.images)
         self.is_animated = self._n_frames > 1
 
+        assert self.fp is not None
         self.__fp = self.fp
         self.seek(0)
 
diff --git a/src/PIL/MpoImagePlugin.py b/src/PIL/MpoImagePlugin.py
index 71f89a09a..02db52af4 100644
--- a/src/PIL/MpoImagePlugin.py
+++ b/src/PIL/MpoImagePlugin.py
@@ -32,6 +32,7 @@ from . import (
     TiffImagePlugin,
 )
 from ._binary import o32le
+from ._util import DeferredError
 
 
 def _save(im: Image.Image, fp: IO[bytes], filename: str | bytes) -> None:
@@ -98,6 +99,7 @@ class MpoImageFile(JpegImagePlugin.JpegImageFile):
     _close_exclusive_fp_after_loading = False
 
     def _open(self) -> None:
+        assert self.fp is not None
         self.fp.seek(0)  # prep the fp in order to pass the JPEG test
         JpegImagePlugin.JpegImageFile._open(self)
         self._after_jpeg_open()
@@ -117,6 +119,7 @@ class MpoImageFile(JpegImagePlugin.JpegImageFile):
         assert self.n_frames == len(self.__mpoffsets)
         del self.info["mpoffset"]  # no longer needed
         self.is_animated = self.n_frames > 1
+        assert self.fp is not None
         self._fp = self.fp  # FIXME: hack
         self._fp.seek(self.__mpoffsets[0])  # get ready to read first frame
         self.__frame = 0
@@ -125,11 +128,15 @@ class MpoImageFile(JpegImagePlugin.JpegImageFile):
         self.readonly = 1
 
     def load_seek(self, pos: int) -> None:
+        if isinstance(self._fp, DeferredError):
+            raise self._fp.ex
         self._fp.seek(pos)
 
     def seek(self, frame: int) -> None:
         if not self._seek_check(frame):
             return
+        if isinstance(self._fp, DeferredError):
+            raise self._fp.ex
         self.fp = self._fp
         self.offset = self.__mpoffsets[frame]
 
diff --git a/src/PIL/PngImagePlugin.py b/src/PIL/PngImagePlugin.py
index c268d7b1a..0887f36fb 100644
--- a/src/PIL/PngImagePlugin.py
+++ b/src/PIL/PngImagePlugin.py
@@ -48,6 +48,7 @@ from ._binary import i32be as i32
 from ._binary import o8
 from ._binary import o16be as o16
 from ._binary import o32be as o32
+from ._util import DeferredError
 
 if TYPE_CHECKING:
     from . import _imaging
@@ -752,6 +753,7 @@ class PngImageFile(ImageFile.ImageFile):
     format_description = "Portable network graphics"
 
     def _open(self) -> None:
+        assert self.fp is not None
         if not _accept(self.fp.read(8)):
             msg = "not a PNG file"
             raise SyntaxError(msg)
@@ -869,6 +871,8 @@ class PngImageFile(ImageFile.ImageFile):
 
     def _seek(self, frame: int, rewind: bool = False) -> None:
         assert self.png is not None
+        if isinstance(self._fp, DeferredError):
+            raise self._fp.ex
 
         self.dispose: _imaging.ImagingCore | None
         dispose_extent = None
@@ -981,6 +985,7 @@ class PngImageFile(ImageFile.ImageFile):
         """internal: read more image data"""
 
         assert self.png is not None
+        assert self.fp is not None
         while self.__idat == 0:
             # end of chunk, skip forward to next one
 
@@ -1014,6 +1019,7 @@ class PngImageFile(ImageFile.ImageFile):
     def load_end(self) -> None:
         """internal: finished reading image data"""
         assert self.png is not None
+        assert self.fp is not None
         if self.__idat != 0:
             self.fp.read(self.__idat)
         while True:
diff --git a/src/PIL/PsdImagePlugin.py b/src/PIL/PsdImagePlugin.py
index 8ff5e3908..eb1c74758 100644
--- a/src/PIL/PsdImagePlugin.py
+++ b/src/PIL/PsdImagePlugin.py
@@ -27,6 +27,7 @@ from ._binary import i16be as i16
 from ._binary import i32be as i32
 from ._binary import si16be as si16
 from ._binary import si32be as si32
+from ._util import DeferredError
 
 MODES = {
     # (photoshop mode, bits) -> (pil mode, required channels)
@@ -60,6 +61,7 @@ class PsdImageFile(ImageFile.ImageFile):
     _close_exclusive_fp_after_loading = False
 
     def _open(self) -> None:
+        assert self.fp is not None
         read = self.fp.read
 
         #
@@ -148,6 +150,8 @@ class PsdImageFile(ImageFile.ImageFile):
     ) -> list[tuple[str, str, tuple[int, int, int, int], list[ImageFile._Tile]]]:
         layers = []
         if self._layers_position is not None:
+            if isinstance(self._fp, DeferredError):
+                raise self._fp.ex
             self._fp.seek(self._layers_position)
             _layer_data = io.BytesIO(ImageFile._safe_read(self._fp, self._layers_size))
             layers = _layerinfo(_layer_data, self._layers_size)
@@ -174,6 +178,8 @@ class PsdImageFile(ImageFile.ImageFile):
             self._mode = mode
             self.tile = tile
             self.frame = layer
+            if isinstance(self._fp, DeferredError):
+                raise self._fp.ex
             self.fp = self._fp
         except IndexError as e:
             msg = "no such layer"
diff --git a/src/PIL/QoiImagePlugin.py b/src/PIL/QoiImagePlugin.py
index 010d3f941..37590f3d3 100644
--- a/src/PIL/QoiImagePlugin.py
+++ b/src/PIL/QoiImagePlugin.py
@@ -22,6 +22,7 @@ class QoiImageFile(ImageFile.ImageFile):
     format_description = "Quite OK Image"
 
     def _open(self) -> None:
+        assert self.fp is not None
         if not _accept(self.fp.read(4)):
             msg = "not a QOI file"
             raise SyntaxError(msg)
diff --git a/src/PIL/SpiderImagePlugin.py b/src/PIL/SpiderImagePlugin.py
index 075073f9f..88dd045d0 100644
--- a/src/PIL/SpiderImagePlugin.py
+++ b/src/PIL/SpiderImagePlugin.py
@@ -40,6 +40,7 @@ import sys
 from typing import IO, TYPE_CHECKING, Any, cast
 
 from . import Image, ImageFile
+from ._util import DeferredError
 
 
 def isInt(f: Any) -> int:
@@ -100,6 +101,7 @@ class SpiderImageFile(ImageFile.ImageFile):
 
     def _open(self) -> None:
         # check header
+        assert self.fp is not None
         n = 27 * 4  # read 27 float values
         f = self.fp.read(n)
 
@@ -181,6 +183,9 @@ class SpiderImageFile(ImageFile.ImageFile):
         if not self._seek_check(frame):
             return
         self.stkoffset = self.hdrlen + frame * (self.hdrlen + self.imgbytes)
+
+        if isinstance(self._fp, DeferredError):
+            raise self._fp.ex
         self.fp = self._fp
         self.fp.seek(self.stkoffset)
         self._open()
@@ -211,26 +216,27 @@ class SpiderImageFile(ImageFile.ImageFile):
 
 
 # given a list of filenames, return a list of images
-def loadImageSeries(filelist: list[str] | None = None) -> list[SpiderImageFile] | None:
+def loadImageSeries(filelist: list[str] | None = None) -> list[Image.Image] | None:
     """create a list of :py:class:`~PIL.Image.Image` objects for use in a montage"""
     if filelist is None or len(filelist) < 1:
         return None
 
-    imglist = []
+    byte_imgs = []
     for img in filelist:
         if not os.path.exists(img):
             print(f"unable to find {img}")
             continue
         try:
             with Image.open(img) as im:
-                im = im.convert2byte()
+                assert isinstance(im, SpiderImageFile)
+                byte_im = im.convert2byte()
         except Exception:
             if not isSpiderImage(img):
                 print(f"{img} is not a Spider image file")
             continue
-        im.info["filename"] = img
-        imglist.append(im)
-    return imglist
+        byte_im.info["filename"] = img
+        byte_imgs.append(byte_im)
+    return byte_imgs
 
 
 # --------------------------------------------------------------------
@@ -321,9 +327,9 @@ if __name__ == "__main__":
             outfile = sys.argv[2]
 
             # perform some image operation
-            im = im.transpose(Image.Transpose.FLIP_LEFT_RIGHT)
+            transposed_im = im.transpose(Image.Transpose.FLIP_LEFT_RIGHT)
             print(
                 f"saving a flipped version of {os.path.basename(filename)} "
                 f"as {outfile} "
             )
-            im.save(outfile, SpiderImageFile.format)
+            transposed_im.save(outfile, SpiderImageFile.format)
diff --git a/src/PIL/TiffImagePlugin.py b/src/PIL/TiffImagePlugin.py
index cc16cbfb0..c9cc65f41 100644
--- a/src/PIL/TiffImagePlugin.py
+++ b/src/PIL/TiffImagePlugin.py
@@ -58,7 +58,7 @@ from ._binary import i32be as i32
 from ._binary import o8
 from ._deprecate import deprecate
 from ._typing import StrOrBytesPath
-from ._util import is_path
+from ._util import DeferredError, is_path
 from .TiffTags import TYPES
 
 if TYPE_CHECKING:
@@ -1154,6 +1154,7 @@ class TiffImageFile(ImageFile.ImageFile):
         """Open the first image in a TIFF file"""
 
         # Header
+        assert self.fp is not None
         ifh = self.fp.read(8)
         if ifh[2] == 43:
             ifh += self.fp.read(8)
@@ -1198,6 +1199,8 @@ class TiffImageFile(ImageFile.ImageFile):
         self.im = Image.core.new(self.mode, self.size)
 
     def _seek(self, frame: int) -> None:
+        if isinstance(self._fp, DeferredError):
+            raise self._fp.ex
         self.fp = self._fp
 
         # reset buffered io handle in case fp
@@ -1283,6 +1286,7 @@ class TiffImageFile(ImageFile.ImageFile):
 
             # reset buffered io handle in case fp
             # was passed to libtiff, invalidating the buffer
+            assert self.fp is not None
             self.fp.tell()
 
             # load IFD data from fp before it is closed
@@ -1316,6 +1320,7 @@ class TiffImageFile(ImageFile.ImageFile):
         # To be nice on memory footprint, if there's a
         # file descriptor, use that instead of reading
         # into a string in python.
+        assert self.fp is not None
         try:
             fp = hasattr(self.fp, "fileno") and self.fp.fileno()
             # flush the file descriptor, prevents error on pypy 2.4+
diff --git a/src/PIL/WalImageFile.py b/src/PIL/WalImageFile.py
index 87e32878b..7e967ff14 100644
--- a/src/PIL/WalImageFile.py
+++ b/src/PIL/WalImageFile.py
@@ -39,6 +39,7 @@ class WalImageFile(ImageFile.ImageFile):
         self._mode = "P"
 
         # read header fields
+        assert self.fp is not None
         header = self.fp.read(32 + 24 + 32 + 12)
         self._size = i32(header, 32), i32(header, 36)
         Image._decompression_bomb_check(self.size)
@@ -55,6 +56,7 @@ class WalImageFile(ImageFile.ImageFile):
 
     def load(self) -> Image.core.PixelAccess | None:
         if self._im is None:
+            assert self.fp is not None
             self.im = Image.core.new(self.mode, self.size)
             self.frombytes(self.fp.read(self.size[0] * self.size[1]))
             self.putpalette(quake2palette)
diff --git a/src/PIL/WebPImagePlugin.py b/src/PIL/WebPImagePlugin.py
index f8d6168ba..343b3892d 100644
--- a/src/PIL/WebPImagePlugin.py
+++ b/src/PIL/WebPImagePlugin.py
@@ -47,6 +47,7 @@ class WebPImageFile(ImageFile.ImageFile):
     def _open(self) -> None:
         # Use the newer AnimDecoder API to parse the (possibly) animated file,
         # and access muxed chunks like ICC/EXIF/XMP.
+        assert self.fp is not None
         self._decoder = _webp.WebPAnimDecoder(self.fp.read())
 
         # Get info from decoder
diff --git a/src/PIL/WmfImagePlugin.py b/src/PIL/WmfImagePlugin.py
index 68f8a74f5..f81cca936 100644
--- a/src/PIL/WmfImagePlugin.py
+++ b/src/PIL/WmfImagePlugin.py
@@ -49,6 +49,7 @@ if hasattr(Image.core, "drawwmf"):
             self.bbox = im.info["wmf_bbox"]
 
         def load(self, im: ImageFile.StubImageFile) -> Image.Image:
+            assert im.fp is not None
             im.fp.seek(0)  # rewind
             return Image.frombytes(
                 "RGB",
@@ -85,6 +86,7 @@ class WmfStubImageFile(ImageFile.StubImageFile):
         self._inch = None
 
         # check placable header
+        assert self.fp is not None
         s = self.fp.read(80)
 
         if s[:6] == b"\xd7\xcd\xc6\x9a\x00\x00":
diff --git a/src/PIL/XVThumbImagePlugin.py b/src/PIL/XVThumbImagePlugin.py
index 5d1f201a4..787bd94a2 100644
--- a/src/PIL/XVThumbImagePlugin.py
+++ b/src/PIL/XVThumbImagePlugin.py
@@ -58,15 +58,15 @@ class XVThumbImageFile(ImageFile.ImageFile):
 
         # skip info comments
         while True:
-            s = self.fp.readline()
-            if not s:
+            line = self.fp.readline()
+            if not line:
                 msg = "Unexpected EOF reading XV thumbnail file"
                 raise SyntaxError(msg)
-            if s[0] != 35:  # ie. when not a comment: '#'
+            if line[0] != 35:  # ie. when not a comment: '#'
                 break
 
         # parse header line (already read)
-        s = s.strip().split()
+        s = line.strip().split()
 
         self._mode = "P"
         self._size = int(s[0]), int(s[1])
diff --git a/src/PIL/XpmImagePlugin.py b/src/PIL/XpmImagePlugin.py
index 1fc6c0c39..019813291 100644
--- a/src/PIL/XpmImagePlugin.py
+++ b/src/PIL/XpmImagePlugin.py
@@ -37,17 +37,18 @@ class XpmImageFile(ImageFile.ImageFile):
     format_description = "X11 Pixel Map"
 
     def _open(self) -> None:
+        assert self.fp is not None
         if not _accept(self.fp.read(9)):
             msg = "not an XPM file"
             raise SyntaxError(msg)
 
         # skip forward to next string
         while True:
-            s = self.fp.readline()
-            if not s:
+            line = self.fp.readline()
+            if not line:
                 msg = "broken XPM file"
                 raise SyntaxError(msg)
-            m = xpm_head.match(s)
+            m = xpm_head.match(line)
             if m:
                 break
 
@@ -66,14 +67,14 @@ class XpmImageFile(ImageFile.ImageFile):
         palette = [b"\0\0\0"] * 256
 
         for _ in range(pal):
-            s = self.fp.readline()
-            if s[-2:] == b"\r\n":
-                s = s[:-2]
-            elif s[-1:] in b"\r\n":
-                s = s[:-1]
+            line = self.fp.readline()
+            if line[-2:] == b"\r\n":
+                line = line[:-2]
+            elif line[-1:] in b"\r\n":
+                line = line[:-1]
 
-            c = s[1]
-            s = s[2:-2].split()
+            c = line[1]
+            s = line[2:-2].split()
 
             for i in range(0, len(s), 2):
                 if s[i] == b"c":
@@ -83,9 +84,11 @@ class XpmImageFile(ImageFile.ImageFile):
                         self.info["transparency"] = c
                     elif rgb[:1] == b"#":
                         # FIXME: handle colour names (see ImagePalette.py)
-                        rgb = int(rgb[1:], 16)
+                        rgb_int = int(rgb[1:], 16)
                         palette[c] = (
-                            o8((rgb >> 16) & 255) + o8((rgb >> 8) & 255) + o8(rgb & 255)
+                            o8((rgb_int >> 16) & 255)
+                            + o8((rgb_int >> 8) & 255)
+                            + o8(rgb_int & 255)
                         )
                     else:
                         # unknown colour
@@ -111,6 +114,7 @@ class XpmImageFile(ImageFile.ImageFile):
 
         xsize, ysize = self.size
 
+        assert self.fp is not None
         s = [self.fp.readline()[1 : xsize + 1].ljust(xsize) for i in range(ysize)]
 
         return b"".join(s)