Use monkeypatch (#8707)

Co-authored-by: Andrew Murray <[email protected]>

Author: radarhere

Tests/check_png_dos.py

@@ -3,26 +3,25 @@
 import zlib
 from io import BytesIO
 
+import pytest
+
 from PIL import Image, ImageFile, PngImagePlugin
 
 TEST_FILE = "Tests/images/png_decompression_dos.png"
 
 
-def test_ignore_dos_text() -> None:
-    ImageFile.LOAD_TRUNCATED_IMAGES = True
+def test_ignore_dos_text(monkeypatch: pytest.MonkeyPatch) -> None:
+    monkeypatch.setattr(ImageFile, "LOAD_TRUNCATED_IMAGES", True)
 
-    try:
-        im = Image.open(TEST_FILE)
+    with Image.open(TEST_FILE) as im:
         im.load()
-    finally:
-        ImageFile.LOAD_TRUNCATED_IMAGES = False
 
-    assert isinstance(im, PngImagePlugin.PngImageFile)
-    for s in im.text.values():
-        assert len(s) < 1024 * 1024, "Text chunk larger than 1M"
+        assert isinstance(im, PngImagePlugin.PngImageFile)
+        for s in im.text.values():
+            assert len(s) < 1024 * 1024, "Text chunk larger than 1M"
 
-    for s in im.info.values():
-        assert len(s) < 1024 * 1024, "Text chunk larger than 1M"
+        for s in im.info.values():
+            assert len(s) < 1024 * 1024, "Text chunk larger than 1M"
 
 
 def test_dos_text() -> None:

Tests/test_decompression_bomb.py

@@ -12,19 +12,16 @@
 
 
 class TestDecompressionBomb:
-    def teardown_method(self) -> None:
-        Image.MAX_IMAGE_PIXELS = ORIGINAL_LIMIT
-
     def test_no_warning_small_file(self) -> None:
         # Implicit assert: no warning.
         # A warning would cause a failure.
         with Image.open(TEST_FILE):
             pass
 
-    def test_no_warning_no_limit(self) -> None:
+    def test_no_warning_no_limit(self, monkeypatch: pytest.MonkeyPatch) -> None:
         # Arrange
         # Turn limit off
-        Image.MAX_IMAGE_PIXELS = None
+        monkeypatch.setattr(Image, "MAX_IMAGE_PIXELS", None)
         assert Image.MAX_IMAGE_PIXELS is None
 
         # Act / Assert
@@ -33,18 +30,18 @@ def test_no_warning_no_limit(self) -> None:
         with Image.open(TEST_FILE):
             pass
 
-    def test_warning(self) -> None:
+    def test_warning(self, monkeypatch: pytest.MonkeyPatch) -> None:
         # Set limit to trigger warning on the test file
-        Image.MAX_IMAGE_PIXELS = 128 * 128 - 1
+        monkeypatch.setattr(Image, "MAX_IMAGE_PIXELS", 128 * 128 - 1)
         assert Image.MAX_IMAGE_PIXELS == 128 * 128 - 1
 
         with pytest.warns(Image.DecompressionBombWarning):
             with Image.open(TEST_FILE):
                 pass
 
-    def test_exception(self) -> None:
+    def test_exception(self, monkeypatch: pytest.MonkeyPatch) -> None:
         # Set limit to trigger exception on the test file
-        Image.MAX_IMAGE_PIXELS = 64 * 128 - 1
+        monkeypatch.setattr(Image, "MAX_IMAGE_PIXELS", 64 * 128 - 1)
         assert Image.MAX_IMAGE_PIXELS == 64 * 128 - 1
 
         with pytest.raises(Image.DecompressionBombError):
@@ -66,9 +63,9 @@ def test_exception_gif_extents(self) -> None:
             with pytest.raises(Image.DecompressionBombError):
                 im.seek(1)
 
-    def test_exception_gif_zero_width(self) -> None:
+    def test_exception_gif_zero_width(self, monkeypatch: pytest.MonkeyPatch) -> None:
         # Set limit to trigger exception on the test file
-        Image.MAX_IMAGE_PIXELS = 4 * 64 * 128
+        monkeypatch.setattr(Image, "MAX_IMAGE_PIXELS", 4 * 64 * 128)
         assert Image.MAX_IMAGE_PIXELS == 4 * 64 * 128
 
         with pytest.raises(Image.DecompressionBombError):

Tests/test_file_fli.py

@@ -35,22 +35,19 @@ def test_sanity() -> None:
         assert im.is_animated
 
 
-def test_prefix_chunk() -> None:
-    ImageFile.LOAD_TRUNCATED_IMAGES = True
-    try:
-        with Image.open(animated_test_file_with_prefix_chunk) as im:
-            assert im.mode == "P"
-            assert im.size == (320, 200)
-            assert im.format == "FLI"
-            assert im.info["duration"] == 171
-            assert im.is_animated
-
-            palette = im.getpalette()
-            assert palette[3:6] == [255, 255, 255]
-            assert palette[381:384] == [204, 204, 12]
-            assert palette[765:] == [252, 0, 0]
-    finally:
-        ImageFile.LOAD_TRUNCATED_IMAGES = False
+def test_prefix_chunk(monkeypatch: pytest.MonkeyPatch) -> None:
+    monkeypatch.setattr(ImageFile, "LOAD_TRUNCATED_IMAGES", True)
+    with Image.open(animated_test_file_with_prefix_chunk) as im:
+        assert im.mode == "P"
+        assert im.size == (320, 200)
+        assert im.format == "FLI"
+        assert im.info["duration"] == 171
+        assert im.is_animated
+
+        palette = im.getpalette()
+        assert palette[3:6] == [255, 255, 255]
+        assert palette[381:384] == [204, 204, 12]
+        assert palette[765:] == [252, 0, 0]
 
 
 @pytest.mark.skipif(is_pypy(), reason="Requires CPython")

Tests/test_file_gif.py

@@ -109,7 +109,7 @@ def test_palette_not_needed_for_second_frame() -> None:
         assert_image_similar(im, hopper("L").convert("RGB"), 8)
 
 
-def test_strategy() -> None:
+def test_strategy(monkeypatch: pytest.MonkeyPatch) -> None:
     with Image.open("Tests/images/iss634.gif") as im:
         expected_rgb_always = im.convert("RGB")
 
@@ -119,35 +119,36 @@ def test_strategy() -> None:
         im.seek(1)
         expected_different = im.convert("RGB")
 
-    try:
-        GifImagePlugin.LOADING_STRATEGY = GifImagePlugin.LoadingStrategy.RGB_ALWAYS
-        with Image.open("Tests/images/iss634.gif") as im:
-            assert im.mode == "RGB"
-            assert_image_equal(im, expected_rgb_always)
+    monkeypatch.setattr(
+        GifImagePlugin, "LOADING_STRATEGY", GifImagePlugin.LoadingStrategy.RGB_ALWAYS
+    )
+    with Image.open("Tests/images/iss634.gif") as im:
+        assert im.mode == "RGB"
+        assert_image_equal(im, expected_rgb_always)
 
-        with Image.open("Tests/images/chi.gif") as im:
-            assert im.mode == "RGBA"
-            assert_image_equal(im, expected_rgb_always_rgba)
+    with Image.open("Tests/images/chi.gif") as im:
+        assert im.mode == "RGBA"
+        assert_image_equal(im, expected_rgb_always_rgba)
 
-        GifImagePlugin.LOADING_STRATEGY = (
-            GifImagePlugin.LoadingStrategy.RGB_AFTER_DIFFERENT_PALETTE_ONLY
-        )
-        # Stay in P mode with only a global palette
-        with Image.open("Tests/images/chi.gif") as im:
-            assert im.mode == "P"
+    monkeypatch.setattr(
+        GifImagePlugin,
+        "LOADING_STRATEGY",
+        GifImagePlugin.LoadingStrategy.RGB_AFTER_DIFFERENT_PALETTE_ONLY,
+    )
+    # Stay in P mode with only a global palette
+    with Image.open("Tests/images/chi.gif") as im:
+        assert im.mode == "P"
 
-            im.seek(1)
-            assert im.mode == "P"
-            assert_image_equal(im.convert("RGB"), expected_different)
+        im.seek(1)
+        assert im.mode == "P"
+        assert_image_equal(im.convert("RGB"), expected_different)
 
-        # Change to RGB mode when a frame has an individual palette
-        with Image.open("Tests/images/iss634.gif") as im:
-            assert im.mode == "P"
+    # Change to RGB mode when a frame has an individual palette
+    with Image.open("Tests/images/iss634.gif") as im:
+        assert im.mode == "P"
 
-            im.seek(1)
-            assert im.mode == "RGB"
-    finally:
-        GifImagePlugin.LOADING_STRATEGY = GifImagePlugin.LoadingStrategy.RGB_AFTER_FIRST
+        im.seek(1)
+        assert im.mode == "RGB"
 
 
 def test_optimize() -> None:
@@ -555,17 +556,15 @@ def test_dispose_background_transparency() -> None:
 def test_transparent_dispose(
     loading_strategy: GifImagePlugin.LoadingStrategy,
     expected_colors: tuple[tuple[int | tuple[int, int, int, int], ...]],
+    monkeypatch: pytest.MonkeyPatch,
 ) -> None:
-    GifImagePlugin.LOADING_STRATEGY = loading_strategy
-    try:
-        with Image.open("Tests/images/transparent_dispose.gif") as img:
-            for frame in range(3):
-                img.seek(frame)
-                for x in range(3):
-                    color = img.getpixel((x, 0))
-                    assert color == expected_colors[frame][x]
-    finally:
-        GifImagePlugin.LOADING_STRATEGY = GifImagePlugin.LoadingStrategy.RGB_AFTER_FIRST
+    monkeypatch.setattr(GifImagePlugin, "LOADING_STRATEGY", loading_strategy)
+    with Image.open("Tests/images/transparent_dispose.gif") as img:
+        for frame in range(3):
+            img.seek(frame)
+            for x in range(3):
+                color = img.getpixel((x, 0))
+                assert color == expected_colors[frame][x]
 
 
 def test_dispose_previous() -> None:
@@ -1398,24 +1397,23 @@ def test_lzw_bits() -> None:
     ),
 )
 def test_extents(
-    test_file: str, loading_strategy: GifImagePlugin.LoadingStrategy
+    test_file: str,
+    loading_strategy: GifImagePlugin.LoadingStrategy,
+    monkeypatch: pytest.MonkeyPatch,
 ) -> None:
-    GifImagePlugin.LOADING_STRATEGY = loading_strategy
-    try:
-        with Image.open("Tests/images/" + test_file) as im:
-            assert im.size == (100, 100)
+    monkeypatch.setattr(GifImagePlugin, "LOADING_STRATEGY", loading_strategy)
+    with Image.open("Tests/images/" + test_file) as im:
+        assert im.size == (100, 100)
 
-            # Check that n_frames does not change the size
-            assert im.n_frames == 2
-            assert im.size == (100, 100)
+        # Check that n_frames does not change the size
+        assert im.n_frames == 2
+        assert im.size == (100, 100)
 
-            im.seek(1)
-            assert im.size == (150, 150)
+        im.seek(1)
+        assert im.size == (150, 150)
 
-            im.load()
-            assert im.im.size == (150, 150)
-    finally:
-        GifImagePlugin.LOADING_STRATEGY = GifImagePlugin.LoadingStrategy.RGB_AFTER_FIRST
+        im.load()
+        assert im.im.size == (150, 150)
 
 
 def test_missing_background() -> None:

Tests/test_file_ico.py

@@ -243,26 +243,23 @@ def test_draw_reloaded(tmp_path: Path) -> None:
         assert_image_equal_tofile(im, "Tests/images/hopper_draw.ico")
 
 
-def test_truncated_mask() -> None:
+def test_truncated_mask(monkeypatch: pytest.MonkeyPatch) -> None:
     # 1 bpp
     with open("Tests/images/hopper_mask.ico", "rb") as fp:
         data = fp.read()
 
-    ImageFile.LOAD_TRUNCATED_IMAGES = True
+    monkeypatch.setattr(ImageFile, "LOAD_TRUNCATED_IMAGES", True)
     data = data[:-3]
 
-    try:
-        with Image.open(io.BytesIO(data)) as im:
-            assert im.mode == "1"
+    with Image.open(io.BytesIO(data)) as im:
+        assert im.mode == "1"
 
-        # 32 bpp
-        output = io.BytesIO()
-        expected = hopper("RGBA")
-        expected.save(output, "ico", bitmap_format="bmp")
+    # 32 bpp
+    output = io.BytesIO()
+    expected = hopper("RGBA")
+    expected.save(output, "ico", bitmap_format="bmp")
 
-        data = output.getvalue()[:-1]
+    data = output.getvalue()[:-1]
 
-        with Image.open(io.BytesIO(data)) as im:
-            assert im.mode == "RGB"
-    finally:
-        ImageFile.LOAD_TRUNCATED_IMAGES = False
+    with Image.open(io.BytesIO(data)) as im:
+        assert im.mode == "RGB"

Tests/test_file_jpeg.py

@@ -530,12 +530,13 @@ def test_ff00_jpeg_header(self) -> None:
     @mark_if_feature_version(
         pytest.mark.valgrind_known_error, "libjpeg_turbo", "2.0", reason="Known Failing"
     )
-    def test_truncated_jpeg_should_read_all_the_data(self) -> None:
+    def test_truncated_jpeg_should_read_all_the_data(
+        self, monkeypatch: pytest.MonkeyPatch
+    ) -> None:
         filename = "Tests/images/truncated_jpeg.jpg"
-        ImageFile.LOAD_TRUNCATED_IMAGES = True
+        monkeypatch.setattr(ImageFile, "LOAD_TRUNCATED_IMAGES", True)
         with Image.open(filename) as im:
             im.load()
-            ImageFile.LOAD_TRUNCATED_IMAGES = False
             assert im.getbbox() is not None
 
     def test_truncated_jpeg_throws_oserror(self) -> None:
@@ -1024,7 +1025,7 @@ def test_save_xmp(self, tmp_path: Path) -> None:
             im.save(f, xmp=b"1" * 65505)
 
     @pytest.mark.timeout(timeout=1)
-    def test_eof(self) -> None:
+    def test_eof(self, monkeypatch: pytest.MonkeyPatch) -> None:
         # Even though this decoder never says that it is finished
         # the image should still end when there is no new data
         class InfiniteMockPyDecoder(ImageFile.PyDecoder):
@@ -1039,9 +1040,8 @@ def decode(
             im.tile = [
                 ImageFile._Tile("INFINITE", (0, 0, 128, 128), 0, ("RGB", 0, 1)),
             ]
-            ImageFile.LOAD_TRUNCATED_IMAGES = True
+            monkeypatch.setattr(ImageFile, "LOAD_TRUNCATED_IMAGES", True)
             im.load()
-            ImageFile.LOAD_TRUNCATED_IMAGES = False
 
     def test_separate_tables(self) -> None:
         im = hopper()

Tests/test_file_jpeg2k.py

@@ -181,14 +181,11 @@ def test_load_dpi() -> None:
         assert "dpi" not in im.info
 
 
-def test_restricted_icc_profile() -> None:
-    ImageFile.LOAD_TRUNCATED_IMAGES = True
-    try:
-        # JPEG2000 image with a restricted ICC profile and a known colorspace
-        with Image.open("Tests/images/balloon_eciRGBv2_aware.jp2") as im:
-            assert im.mode == "RGB"
-    finally:
-        ImageFile.LOAD_TRUNCATED_IMAGES = False
+def test_restricted_icc_profile(monkeypatch: pytest.MonkeyPatch) -> None:
+    monkeypatch.setattr(ImageFile, "LOAD_TRUNCATED_IMAGES", True)
+    # JPEG2000 image with a restricted ICC profile and a known colorspace
+    with Image.open("Tests/images/balloon_eciRGBv2_aware.jp2") as im:
+        assert im.mode == "RGB"
 
 
 @pytest.mark.skipif(

Tests/test_file_libtiff.py

@@ -1156,23 +1156,22 @@ def test_save_multistrip(self, compression: str, tmp_path: Path) -> None:
             assert len(im.tag_v2[STRIPOFFSETS]) > 1
 
     @pytest.mark.parametrize("argument", (True, False))
-    def test_save_single_strip(self, argument: bool, tmp_path: Path) -> None:
+    def test_save_single_strip(
+        self, argument: bool, tmp_path: Path, monkeypatch: pytest.MonkeyPatch
+    ) -> None:
         im = hopper("RGB").resize((256, 256))
         out = str(tmp_path / "temp.tif")
 
         if not argument:
-            TiffImagePlugin.STRIP_SIZE = 2**18
-        try:
-            arguments: dict[str, str | int] = {"compression": "tiff_adobe_deflate"}
-            if argument:
-                arguments["strip_size"] = 2**18
-            im.save(out, "TIFF", **arguments)
-
-            with Image.open(out) as im:
-                assert isinstance(im, TiffImagePlugin.TiffImageFile)
-                assert len(im.tag_v2[STRIPOFFSETS]) == 1
-        finally:
-            TiffImagePlugin.STRIP_SIZE = 65536
+            monkeypatch.setattr(TiffImagePlugin, "STRIP_SIZE", 2**18)
+        arguments: dict[str, str | int] = {"compression": "tiff_adobe_deflate"}
+        if argument:
+            arguments["strip_size"] = 2**18
+        im.save(out, "TIFF", **arguments)
+
+        with Image.open(out) as im:
+            assert isinstance(im, TiffImagePlugin.TiffImageFile)
+            assert len(im.tag_v2[STRIPOFFSETS]) == 1
 
     @pytest.mark.parametrize("compression", ("tiff_adobe_deflate", None))
     def test_save_zero(self, compression: str | None, tmp_path: Path) -> None: