mcidas test case changes implemented

Tests/test_file_mcidas.py

@@ -1,32 +1,79 @@
 from __future__ import annotations
 
 import pytest
-
 from PIL import Image, McIdasImagePlugin
-
 from .helper import assert_image_equal_tofile
+from io import BytesIO
+import struct
 
+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
+
+    # 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
+    with Image.open(test_file) as im:
+        im.load()
+        # Assert
+        assert im.format == "MCIDAS"
+        assert im.mode == "L"
+        assert im.size == (1800, 400)
+
+def test_32bit_file() -> None:
+    # Arrange
+    test_file = create_mock_mcidas_file(4)
+
+    # Act
+    with Image.open(test_file) as im:
+        im.load()
+        # Assert
+        assert im.format == "MCIDAS"
+        assert im.mode == "I"
+        assert im.size == (1800, 400)
+
+def test_unsupported_file() -> None:
+    # Arrange
+    test_file = create_mock_mcidas_file(3)
+
+    # Act & Assert
+    with pytest.raises(SyntaxError, match="unsupported McIdas format"):
+        Image.open(test_file)