diff --git a/Tests/test_deprecate.py b/Tests/test_deprecate.py
index 6ffc8f6f5..584d8f91d 100644
--- a/Tests/test_deprecate.py
+++ b/Tests/test_deprecate.py
@@ -20,7 +20,7 @@ from PIL import _deprecate
         ),
     ],
 )
-def test_version(version, expected) -> None:
+def test_version(version: int | None, expected: str) -> None:
     with pytest.warns(DeprecationWarning, match=expected):
         _deprecate.deprecate("Old thing", version, "new thing")
 
@@ -46,7 +46,7 @@ def test_unknown_version() -> None:
         ),
     ],
 )
-def test_old_version(deprecated, plural, expected) -> None:
+def test_old_version(deprecated: str, plural: bool, expected: str) -> None:
     expected = r""
     with pytest.raises(RuntimeError, match=expected):
         _deprecate.deprecate(deprecated, 1, plural=plural)
@@ -76,7 +76,7 @@ def test_replacement_and_action() -> None:
         "Upgrade to new thing.",
     ],
 )
-def test_action(action) -> None:
+def test_action(action: str) -> None:
     expected = (
         r"Old thing is deprecated and will be removed in Pillow 11 \(2024-10-15\)\. "
         r"Upgrade to new thing\."
diff --git a/Tests/test_file_ico.py b/Tests/test_file_ico.py
index 65f090931..f69a290fa 100644
--- a/Tests/test_file_ico.py
+++ b/Tests/test_file_ico.py
@@ -135,7 +135,7 @@ def test_different_bit_depths(tmp_path: Path) -> None:
 
 
 @pytest.mark.parametrize("mode", ("1", "L", "P", "RGB", "RGBA"))
-def test_save_to_bytes_bmp(mode) -> None:
+def test_save_to_bytes_bmp(mode: str) -> None:
     output = io.BytesIO()
     im = hopper(mode)
     im.save(output, "ico", bitmap_format="bmp", sizes=[(32, 32), (64, 64)])
diff --git a/Tests/test_file_iptc.py b/Tests/test_file_iptc.py
index 9c0969437..88c30d468 100644
--- a/Tests/test_file_iptc.py
+++ b/Tests/test_file_iptc.py
@@ -98,7 +98,7 @@ def test_i() -> None:
     assert ret == 97
 
 
-def test_dump(monkeypatch) -> None:
+def test_dump(monkeypatch: pytest.MonkeyPatch) -> None:
     # Arrange
     c = b"abc"
     # Temporarily redirect stdout
diff --git a/Tests/test_file_msp.py b/Tests/test_file_msp.py
index f9f81d114..b0964aabe 100644
--- a/Tests/test_file_msp.py
+++ b/Tests/test_file_msp.py
@@ -52,7 +52,7 @@ def test_open_windows_v1() -> None:
         assert isinstance(im, MspImagePlugin.MspImageFile)
 
 
-def _assert_file_image_equal(source_path, target_path) -> None:
+def _assert_file_image_equal(source_path: str, target_path: str) -> None:
     with Image.open(source_path) as im:
         assert_image_equal_tofile(im, target_path)
 
diff --git a/Tests/test_file_png.py b/Tests/test_file_png.py
index d4a634316..c51f56ce7 100644
--- a/Tests/test_file_png.py
+++ b/Tests/test_file_png.py
@@ -6,6 +6,7 @@ import warnings
 import zlib
 from io import BytesIO
 from pathlib import Path
+from types import ModuleType
 from typing import Any
 
 import pytest
@@ -23,6 +24,7 @@ from .helper import (
     skip_unless_feature,
 )
 
+ElementTree: ModuleType | None
 try:
     from defusedxml import ElementTree
 except ImportError:
diff --git a/Tests/test_file_psd.py b/Tests/test_file_psd.py
index 7eca8d9b1..e60638b22 100644
--- a/Tests/test_file_psd.py
+++ b/Tests/test_file_psd.py
@@ -157,7 +157,7 @@ def test_combined_larger_than_size() -> None:
         ("Tests/images/timeout-dedc7a4ebd856d79b4359bbcc79e8ef231ce38f6.psd", OSError),
     ],
 )
-def test_crashes(test_file, raises) -> None:
+def test_crashes(test_file: str, raises) -> None:
     with open(test_file, "rb") as f:
         with pytest.raises(raises):
             with Image.open(f):
diff --git a/Tests/test_file_tga.py b/Tests/test_file_tga.py
index bd8e522c7..3c6da50c5 100644
--- a/Tests/test_file_tga.py
+++ b/Tests/test_file_tga.py
@@ -22,8 +22,8 @@ _ORIGIN_TO_ORIENTATION = {"tl": 1, "bl": -1}
 
 
 @pytest.mark.parametrize("mode", _MODES)
-def test_sanity(mode, tmp_path: Path) -> None:
-    def roundtrip(original_im) -> None:
+def test_sanity(mode: str, tmp_path: Path) -> None:
+    def roundtrip(original_im: Image.Image) -> None:
         out = str(tmp_path / "temp.tga")
 
         original_im.save(out, rle=rle)
diff --git a/Tests/test_file_tiff_metadata.py b/Tests/test_file_tiff_metadata.py
index bb6225d07..d7a18c725 100644
--- a/Tests/test_file_tiff_metadata.py
+++ b/Tests/test_file_tiff_metadata.py
@@ -189,7 +189,9 @@ def test_iptc(tmp_path: Path) -> None:
 
 
 @pytest.mark.parametrize("value, expected", ((b"test", "test"), (1, "1")))
-def test_writing_other_types_to_ascii(value, expected, tmp_path: Path) -> None:
+def test_writing_other_types_to_ascii(
+    value: bytes | int, expected: str, tmp_path: Path
+) -> None:
     info = TiffImagePlugin.ImageFileDirectory_v2()
 
     tag = TiffTags.TAGS_V2[271]
@@ -206,7 +208,7 @@ def test_writing_other_types_to_ascii(value, expected, tmp_path: Path) -> None:
 
 
 @pytest.mark.parametrize("value", (1, IFDRational(1)))
-def test_writing_other_types_to_bytes(value, tmp_path: Path) -> None:
+def test_writing_other_types_to_bytes(value: int | IFDRational, tmp_path: Path) -> None:
     im = hopper()
     info = TiffImagePlugin.ImageFileDirectory_v2()
 
diff --git a/Tests/test_imagecms.py b/Tests/test_imagecms.py
index 83fc38ed3..21a0dd75b 100644
--- a/Tests/test_imagecms.py
+++ b/Tests/test_imagecms.py
@@ -237,7 +237,7 @@ def test_invalid_color_temperature() -> None:
 
 
 @pytest.mark.parametrize("flag", ("my string", -1))
-def test_invalid_flag(flag) -> None:
+def test_invalid_flag(flag: str | int) -> None:
     with hopper() as im:
         with pytest.raises(
             ImageCms.PyCMSError, match="flags must be an integer between 0 and "
@@ -335,12 +335,26 @@ def test_extended_information() -> None:
     o = ImageCms.getOpenProfile(SRGB)
     p = o.profile
 
-    def assert_truncated_tuple_equal(tup1, tup2, digits: int = 10) -> None:
+    def assert_truncated_tuple_equal(
+        tup1: tuple[tuple[float, float, float], ...] | tuple[float],
+        tup2: (
+            tuple[tuple[tuple[float, float, float], ...], ...]
+            | tuple[tuple[float, float, float], ...]
+            | tuple[float]
+        ),
+        digits: int = 10,
+    ) -> None:
         # Helper function to reduce precision of tuples of floats
         # recursively and then check equality.
         power = 10**digits
 
-        def truncate_tuple(tuple_or_float):
+        def truncate_tuple(
+            tuple_or_float: (
+                tuple[tuple[tuple[float, float, float], ...], ...]
+                | tuple[tuple[float, float, float], ...]
+                | tuple[float, ...]
+            )
+        ) -> tuple[tuple[float, ...], ...]:
             return tuple(
                 (
                     truncate_tuple(val)
@@ -504,8 +518,10 @@ def test_profile_typesafety() -> None:
         ImageCms.ImageCmsProfile(1).tobytes()
 
 
-def assert_aux_channel_preserved(mode, transform_in_place, preserved_channel) -> None:
-    def create_test_image():
+def assert_aux_channel_preserved(
+    mode: str, transform_in_place: bool, preserved_channel: str
+) -> None:
+    def create_test_image() -> Image.Image:
         # set up test image with something interesting in the tested aux channel.
         # fmt: off
         nine_grid_deltas = [
@@ -633,7 +649,7 @@ def test_auxiliary_channels_isolated() -> None:
 
 
 @pytest.mark.parametrize("mode", ("RGB", "RGBA", "RGBX"))
-def test_rgb_lab(mode) -> None:
+def test_rgb_lab(mode: str) -> None:
     im = Image.new(mode, (1, 1))
     converted_im = im.convert("LAB")
     assert converted_im.getpixel((0, 0)) == (0, 128, 128)
diff --git a/Tests/test_imagefont.py b/Tests/test_imagefont.py
index c79b36ca4..05b5d4716 100644
--- a/Tests/test_imagefont.py
+++ b/Tests/test_imagefont.py
@@ -7,7 +7,7 @@ import shutil
 import sys
 from io import BytesIO
 from pathlib import Path
-from typing import BinaryIO
+from typing import Any, BinaryIO
 
 import pytest
 from packaging.version import parse as parse_version
@@ -44,7 +44,7 @@ def test_sanity() -> None:
         pytest.param(ImageFont.Layout.RAQM, marks=skip_unless_feature("raqm")),
     ],
 )
-def layout_engine(request):
+def layout_engine(request: pytest.FixtureRequest) -> ImageFont.Layout:
     return request.param
 
 
@@ -535,21 +535,23 @@ def test_unicode_extended(layout_engine: ImageFont.Layout) -> None:
     (("linux", "/usr/local/share/fonts"), ("darwin", "/System/Library/Fonts")),
 )
 @pytest.mark.skipif(is_win32(), reason="requires Unix or macOS")
-def test_find_font(monkeypatch, platform, font_directory) -> None:
+def test_find_font(
+    monkeypatch: pytest.MonkeyPatch, platform: str, font_directory: str
+) -> None:
     def _test_fake_loading_font(path_to_fake: str, fontname: str) -> None:
         # Make a copy of FreeTypeFont so we can patch the original
         free_type_font = copy.deepcopy(ImageFont.FreeTypeFont)
         with monkeypatch.context() as m:
             m.setattr(ImageFont, "_FreeTypeFont", free_type_font, raising=False)
 
-            def loadable_font(filepath, size, index, encoding, *args, **kwargs):
+            def loadable_font(
+                filepath: str, size: int, index: int, encoding: str, *args: Any
+            ):
                 if filepath == path_to_fake:
                     return ImageFont._FreeTypeFont(
-                        FONT_PATH, size, index, encoding, *args, **kwargs
+                        FONT_PATH, size, index, encoding, *args
                     )
-                return ImageFont._FreeTypeFont(
-                    filepath, size, index, encoding, *args, **kwargs
-                )
+                return ImageFont._FreeTypeFont(filepath, size, index, encoding, *args)
 
             m.setattr(ImageFont, "FreeTypeFont", loadable_font)
             font = ImageFont.truetype(fontname)
@@ -563,7 +565,7 @@ def test_find_font(monkeypatch, platform, font_directory) -> None:
     if platform == "linux":
         monkeypatch.setenv("XDG_DATA_DIRS", "/usr/share/:/usr/local/share/")
 
-    def fake_walker(path):
+    def fake_walker(path: str) -> list[tuple[str, list[str], list[str]]]:
         if path == font_directory:
             return [
                 (
@@ -1101,7 +1103,7 @@ def test_oom(test_file: str) -> None:
             font.getmask("Test Text")
 
 
-def test_raqm_missing_warning(monkeypatch) -> None:
+def test_raqm_missing_warning(monkeypatch: pytest.MonkeyPatch) -> None:
     monkeypatch.setattr(ImageFont.core, "HAVE_RAQM", False)
     with pytest.warns(UserWarning) as record:
         font = ImageFont.truetype(
diff --git a/Tests/test_imagegrab.py b/Tests/test_imagegrab.py
index 235a2f993..e23adeb70 100644
--- a/Tests/test_imagegrab.py
+++ b/Tests/test_imagegrab.py
@@ -84,6 +84,7 @@ $bmp = New-Object Drawing.Bitmap 200, 200
     @pytest.mark.skipif(sys.platform != "win32", reason="Windows only")
     def test_grabclipboard_file(self) -> None:
         p = subprocess.Popen(["powershell", "-command", "-"], stdin=subprocess.PIPE)
+        assert p.stdin is not None
         p.stdin.write(rb'Set-Clipboard -Path "Tests\images\hopper.gif"')
         p.communicate()
 
@@ -94,6 +95,7 @@ $bmp = New-Object Drawing.Bitmap 200, 200
     @pytest.mark.skipif(sys.platform != "win32", reason="Windows only")
     def test_grabclipboard_png(self) -> None:
         p = subprocess.Popen(["powershell", "-command", "-"], stdin=subprocess.PIPE)
+        assert p.stdin is not None
         p.stdin.write(
             rb"""$bytes = [System.IO.File]::ReadAllBytes("Tests\images\hopper.png")
 $ms = new-object System.IO.MemoryStream(, $bytes)
@@ -113,7 +115,7 @@ $ms = new-object System.IO.MemoryStream(, $bytes)
         reason="Linux with wl-clipboard only",
     )
     @pytest.mark.parametrize("ext", ("gif", "png", "ico"))
-    def test_grabclipboard_wl_clipboard(self, ext) -> None:
+    def test_grabclipboard_wl_clipboard(self, ext: str) -> None:
         image_path = "Tests/images/hopper." + ext
         with open(image_path, "rb") as fp:
             subprocess.call(["wl-copy"], stdin=fp)
@@ -128,6 +130,6 @@ $ms = new-object System.IO.MemoryStream(, $bytes)
         reason="Linux with wl-clipboard only",
     )
     @pytest.mark.parametrize("arg", ("text", "--clear"))
-    def test_grabclipboard_wl_clipboard_errors(self, arg):
+    def test_grabclipboard_wl_clipboard_errors(self, arg: str) -> None:
         subprocess.call(["wl-copy", arg])
         assert ImageGrab.grabclipboard() is None
diff --git a/Tests/test_imagepath.py b/Tests/test_imagepath.py
index bd600b177..9487560af 100644
--- a/Tests/test_imagepath.py
+++ b/Tests/test_imagepath.py
@@ -58,7 +58,9 @@ def test_path() -> None:
         ImagePath.Path((0, 1)),
     ),
 )
-def test_path_constructors(coords) -> None:
+def test_path_constructors(
+    coords: Sequence[float] | array.array[float] | ImagePath.Path,
+) -> None:
     # Arrange / Act
     p = ImagePath.Path(coords)
 
@@ -206,9 +208,9 @@ class Evil:
     def __init__(self) -> None:
         self.corrupt = Image.core.path(0x4000000000000000)
 
-    def __getitem__(self, i):
+    def __getitem__(self, i: int) -> bytes:
         x = self.corrupt[i]
         return struct.pack("dd", x[0], x[1])
 
-    def __setitem__(self, i, x) -> None:
+    def __setitem__(self, i: int, x: bytes) -> None:
         self.corrupt[i] = struct.unpack("dd", x)
diff --git a/Tests/test_imageqt.py b/Tests/test_imageqt.py
index 909f97167..88ad1f9ee 100644
--- a/Tests/test_imageqt.py
+++ b/Tests/test_imageqt.py
@@ -28,7 +28,7 @@ def test_rgb() -> None:
 
     assert qRgb(0, 0, 0) == qRgba(0, 0, 0, 255)
 
-    def checkrgb(r, g, b) -> None:
+    def checkrgb(r: int, g: int, b: int) -> None:
         val = ImageQt.rgb(r, g, b)
         val = val % 2**24  # drop the alpha
         assert val >> 16 == r
diff --git a/Tests/test_imageshow.py b/Tests/test_imageshow.py
index f7269d45b..8d741d94a 100644
--- a/Tests/test_imageshow.py
+++ b/Tests/test_imageshow.py
@@ -1,5 +1,7 @@
 from __future__ import annotations
 
+from typing import Any
+
 import pytest
 
 from PIL import Image, ImageShow
@@ -24,9 +26,9 @@ def test_register() -> None:
     "order",
     [-1, 0],
 )
-def test_viewer_show(order) -> None:
+def test_viewer_show(order: int) -> None:
     class TestViewer(ImageShow.Viewer):
-        def show_image(self, image, **options) -> bool:
+        def show_image(self, image: Image.Image, **options: Any) -> bool:
             self.methodCalled = True
             return True
 
@@ -48,7 +50,7 @@ def test_viewer_show(order) -> None:
     reason="Only run on CIs; hangs on Windows CIs",
 )
 @pytest.mark.parametrize("mode", ("1", "I;16", "LA", "RGB", "RGBA"))
-def test_show(mode) -> None:
+def test_show(mode: str) -> None:
     im = hopper(mode)
     assert ImageShow.show(im)
 
@@ -73,7 +75,7 @@ def test_viewer() -> None:
 
 
 @pytest.mark.parametrize("viewer", ImageShow._viewers)
-def test_viewers(viewer) -> None:
+def test_viewers(viewer: ImageShow.Viewer) -> None:
     try:
         viewer.get_command("test.jpg")
     except NotImplementedError:
diff --git a/Tests/test_imagewin_pointers.py b/Tests/test_imagewin_pointers.py
index c7f633e62..f59ee7284 100644
--- a/Tests/test_imagewin_pointers.py
+++ b/Tests/test_imagewin_pointers.py
@@ -70,7 +70,7 @@ if is_win32():
     ]
     CreateDIBSection.restype = ctypes.wintypes.HBITMAP
 
-    def serialize_dib(bi, pixels):
+    def serialize_dib(bi, pixels) -> bytearray:
         bf = BITMAPFILEHEADER()
         bf.bfType = 0x4D42
         bf.bfOffBits = ctypes.sizeof(bf) + bi.biSize
diff --git a/Tests/test_numpy.py b/Tests/test_numpy.py
index 6ba95c2d7..9f4e6534e 100644
--- a/Tests/test_numpy.py
+++ b/Tests/test_numpy.py
@@ -14,7 +14,7 @@ TEST_IMAGE_SIZE = (10, 10)
 
 
 def test_numpy_to_image() -> None:
-    def to_image(dtype, bands: int = 1, boolean: int = 0):
+    def to_image(dtype, bands: int = 1, boolean: int = 0) -> Image.Image:
         if bands == 1:
             if boolean:
                 data = [0, 255] * 50
@@ -99,7 +99,7 @@ def test_1d_array() -> None:
     assert_image(Image.fromarray(a), "L", (1, 5))
 
 
-def _test_img_equals_nparray(img, np) -> None:
+def _test_img_equals_nparray(img: Image.Image, np) -> None:
     assert len(np.shape) >= 2
     np_size = np.shape[1], np.shape[0]
     assert img.size == np_size
@@ -157,7 +157,7 @@ def test_save_tiff_uint16() -> None:
         ("HSV", numpy.uint8),
     ),
 )
-def test_to_array(mode, dtype) -> None:
+def test_to_array(mode: str, dtype) -> None:
     img = hopper(mode)
 
     # Resize to non-square
diff --git a/Tests/test_qt_image_qapplication.py b/Tests/test_qt_image_qapplication.py
index 7d6c0a8cb..3cd323553 100644
--- a/Tests/test_qt_image_qapplication.py
+++ b/Tests/test_qt_image_qapplication.py
@@ -4,7 +4,7 @@ from pathlib import Path
 
 import pytest
 
-from PIL import ImageQt
+from PIL import Image, ImageQt
 
 from .helper import assert_image_equal_tofile, assert_image_similar, hopper
 
@@ -37,7 +37,7 @@ if ImageQt.qt_is_installed:
             lbl.setPixmap(pixmap1.copy())
 
 
-def roundtrip(expected) -> None:
+def roundtrip(expected: Image.Image) -> None:
     result = ImageQt.fromqpixmap(ImageQt.toqpixmap(expected))
     # Qt saves all pixmaps as rgb
     assert_image_similar(result, expected.convert("RGB"), 1)
diff --git a/Tests/test_qt_image_toqimage.py b/Tests/test_qt_image_toqimage.py
index a222a7d71..6110be707 100644
--- a/Tests/test_qt_image_toqimage.py
+++ b/Tests/test_qt_image_toqimage.py
@@ -17,7 +17,7 @@ if ImageQt.qt_is_installed:
 
 
 @pytest.mark.parametrize("mode", ("RGB", "RGBA", "L", "P", "1"))
-def test_sanity(mode, tmp_path: Path) -> None:
+def test_sanity(mode: str, tmp_path: Path) -> None:
     src = hopper(mode)
     data = ImageQt.toqimage(src)
 
diff --git a/Tests/test_util.py b/Tests/test_util.py
index 73e4acd55..197ef79ee 100644
--- a/Tests/test_util.py
+++ b/Tests/test_util.py
@@ -10,7 +10,7 @@ from PIL import _util
 @pytest.mark.parametrize(
     "test_path", ["filename.ext", Path("filename.ext"), PurePath("filename.ext")]
 )
-def test_is_path(test_path) -> None:
+def test_is_path(test_path: str | Path | PurePath) -> None:
     # Act
     it_is = _util.is_path(test_path)