diff --git a/Tests/test_file_mcidas.py b/Tests/test_file_mcidas.py
index 8a010bc00..69bfd653c 100644
--- a/Tests/test_file_mcidas.py
+++ b/Tests/test_file_mcidas.py
@@ -1,79 +1,92 @@
 from __future__ import annotations
 
-import pytest
-from PIL import Image, McIdasImagePlugin
-from .helper import assert_image_equal_tofile
-from io import BytesIO
 import struct
+import pytest
 
-def create_mock_mcidas_file(w11_value: int) -> BytesIO:
-    """
-    Creates a mock McIdas file with a given w[11] value.
-    """
-    header = struct.pack(
-        "!64i",
-        0, 0, 0, 0, 0, 0, 0, 4,  # Prefix (first 8 bytes)
-        0, 400, 1800,  # Width, Height (w[9], w[10])
-        w11_value,  # Mode (w[11])
-        0, 0, 0,  # w[12] to w[14]
-        16,  # w[15] (assuming some stride value)
-        0, 0, 0, 0, 0, 0, 0, 0, 0, 0,  # w[16] to w[25]
-        0, 0, 0, 0, 0, 0, 0, 0, 0, 0,  # w[26] to w[35]
-        256,  # w[34] (assuming some offset)
-    )
-    # Ensure header length is 256 bytes
-    header = b"\x00" * (256 - len(header)) + header
+from PIL import Image, McIdasImagePlugin
+
+from .helper import assert_image_equal_tofile
+
+
+def create_mock_file(filename: str, w11_value: int, width: int, height: int) -> None:
+    """
+    Create a mock McIdas area file with specified w[11] value, width, and height.
+    """
+    area_descriptor = [0] * 64
+    area_descriptor[10] = width
+    area_descriptor[9] = height
+    area_descriptor[11] = w11_value
+    area_descriptor[34] = 256  # arbitrary valid offset
+    area_descriptor[15] = 0  # stride (arbitrary valid value)
+    header = b"\x00" * 8 + struct.pack("!64i", *area_descriptor)
+
+    with open(filename, "wb") as f:
+        f.write(header)
+        # Write image data (size based on width, height, and mode)
+        if w11_value == 1:
+            f.write(b"\x00" * (width * height))  # 8-bit data for mode L
+        elif w11_value == 2:
+            f.write(b"\x00" * (2 * width * height))  # 16-bit data for mode I;16B
+        elif w11_value == 4:
+            f.write(b"\x00" * (4 * width * height))  # 32-bit data for mode I;32B
 
-    # Create a valid file
-    return BytesIO(header)
 
 def test_invalid_file() -> None:
     invalid_file = "Tests/images/flower.jpg"
+
     with pytest.raises(SyntaxError):
         McIdasImagePlugin.McIdasImageFile(invalid_file)
 
+
 def test_valid_file() -> None:
     # Arrange
+    # https://ghrc.nsstc.nasa.gov/hydro/details/cmx3g8
+    # https://ghrc.nsstc.nasa.gov/pub/fieldCampaigns/camex3/cmx3g8/browse/
     test_file = "Tests/images/cmx3g8_wv_1998.260_0745_mcidas.ara"
     saved_file = "Tests/images/cmx3g8_wv_1998.260_0745_mcidas.tiff"
 
     # Act
     with Image.open(test_file) as im:
         im.load()
+
         # Assert
         assert im.format == "MCIDAS"
         assert im.mode == "I"
         assert im.size == (1800, 400)
         assert_image_equal_tofile(im, saved_file)
 
-def test_8bit_file() -> None:
-    # Arrange
-    test_file = create_mock_mcidas_file(1)
 
-    # Act
+def test_mode_L() -> None:
+    test_file = "Tests/images/mcidas_mode_L.ara"
+
+    # Create mock file for mode L
+    create_mock_file(test_file, w11_value=1, width=100, height=100)
+
     with Image.open(test_file) as im:
         im.load()
-        # Assert
         assert im.format == "MCIDAS"
         assert im.mode == "L"
-        assert im.size == (1800, 400)
+        assert im.size == (100, 100)
 
-def test_32bit_file() -> None:
-    # Arrange
-    test_file = create_mock_mcidas_file(4)
 
-    # Act
+def test_mode_I_32B() -> None:
+    test_file = "Tests/images/mcidas_mode_I_32B.ara"
+
+    # Create mock file for mode I;32B
+    create_mock_file(test_file, w11_value=4, width=100, height=100)
+
     with Image.open(test_file) as im:
         im.load()
-        # Assert
         assert im.format == "MCIDAS"
         assert im.mode == "I"
-        assert im.size == (1800, 400)
+        assert im.size == (100, 100)
 
-def test_unsupported_file() -> None:
-    # Arrange
-    test_file = create_mock_mcidas_file(3)
 
-    # Act & Assert
+def test_unsupported_format() -> None:
+    test_file = "Tests/images/mcidas_unsupported.ara"
+
+    # Create mock file for unsupported format
+    create_mock_file(test_file, w11_value=3, width=100, height=100)
+
     with pytest.raises(SyntaxError, match="unsupported McIdas format"):
-        Image.open(test_file)
+        McIdasImagePlugin.McIdasImageFile(test_file)