Use monkeypatch to set READ_LIBTIFF and WRITE_LIBTIFF

Tests/test_file_libtiff.py

@@ -185,7 +185,9 @@ def test_write_metadata(self, legacy_api: bool, tmp_path: Path) -> None:
             assert field in reloaded, f"{field} not in metadata"
 
     @pytest.mark.valgrind_known_error(reason="Known invalid metadata")
-    def test_additional_metadata(self, tmp_path: Path) -> None:
+    def test_additional_metadata(
+        self, monkeypatch: pytest.MonkeyPatch, tmp_path: Path
+    ) -> None:
         # these should not crash. Seriously dummy data, most of it doesn't make
         # any sense, so we're running up against limits where we're asking
         # libtiff to do stupid things.
@@ -236,12 +238,10 @@ def test_additional_metadata(self, tmp_path: Path) -> None:
             del new_ifd[338]
 
             out = str(tmp_path / "temp.tif")
-            TiffImagePlugin.WRITE_LIBTIFF = True
+            monkeypatch.setattr(TiffImagePlugin, "WRITE_LIBTIFF", True)
 
             im.save(out, tiffinfo=new_ifd)
 
-        TiffImagePlugin.WRITE_LIBTIFF = False
-
     def test_custom_metadata(self, tmp_path: Path) -> None:
         class Tc(NamedTuple):
             value: Any
@@ -343,24 +343,24 @@ def test_subifd(self, tmp_path: Path) -> None:
             # Should not segfault
             im.save(outfile)
 
-    def test_xmlpacket_tag(self, tmp_path: Path) -> None:
-        TiffImagePlugin.WRITE_LIBTIFF = True
+    def test_xmlpacket_tag(
+        self, monkeypatch: pytest.MonkeyPatch, tmp_path: Path
+    ) -> None:
+        monkeypatch.setattr(TiffImagePlugin, "WRITE_LIBTIFF", True)
 
         out = str(tmp_path / "temp.tif")
         hopper().save(out, tiffinfo={700: b"xmlpacket tag"})
-        TiffImagePlugin.WRITE_LIBTIFF = False
 
         with Image.open(out) as reloaded:
             if 700 in reloaded.tag_v2:
                 assert reloaded.tag_v2[700] == b"xmlpacket tag"
 
-    def test_int_dpi(self, tmp_path: Path) -> None:
+    def test_int_dpi(self, monkeypatch: pytest.MonkeyPatch, tmp_path: Path) -> None:
         # issue #1765
         im = hopper("RGB")
         out = str(tmp_path / "temp.tif")
-        TiffImagePlugin.WRITE_LIBTIFF = True
+        monkeypatch.setattr(TiffImagePlugin, "WRITE_LIBTIFF", True)
         im.save(out, dpi=(72, 72))
-        TiffImagePlugin.WRITE_LIBTIFF = False
         with Image.open(out) as reloaded:
             assert reloaded.info["dpi"] == (72.0, 72.0)
 
@@ -422,13 +422,13 @@ def test_g4_string_info(self, tmp_path: Path) -> None:
             assert "temp.tif" == reread.tag_v2[269]
             assert "temp.tif" == reread.tag[269][0]
 
-    def test_12bit_rawmode(self) -> None:
+    def test_12bit_rawmode(self, monkeypatch: pytest.MonkeyPatch) -> None:
         """Are we generating the same interpretation
         of the image as Imagemagick is?"""
-        TiffImagePlugin.READ_LIBTIFF = True
+        monkeypatch.setattr(TiffImagePlugin, "READ_LIBTIFF", True)
         with Image.open("Tests/images/12bit.cropped.tif") as im:
             im.load()
-            TiffImagePlugin.READ_LIBTIFF = False
+            monkeypatch.setattr(TiffImagePlugin, "READ_LIBTIFF", False)
             # to make the target --
             # convert 12bit.cropped.tif -depth 16 tmp.tif
             # convert tmp.tif -evaluate RightShift 4 12in16bit2.tif
@@ -514,12 +514,13 @@ def test_cmyk_save(self, tmp_path: Path) -> None:
         assert_image_equal_tofile(im, out)
 
     @pytest.mark.parametrize("im", (hopper("P"), Image.new("P", (1, 1), "#000")))
-    def test_palette_save(self, im: Image.Image, tmp_path: Path) -> None:
+    def test_palette_save(
+        self, im: Image.Image, monkeypatch: pytest.MonkeyPatch, tmp_path: Path
+    ) -> None:
         out = str(tmp_path / "temp.tif")
 
-        TiffImagePlugin.WRITE_LIBTIFF = True
+        monkeypatch.setattr(TiffImagePlugin, "WRITE_LIBTIFF", True)
         im.save(out)
-        TiffImagePlugin.WRITE_LIBTIFF = False
 
         with Image.open(out) as reloaded:
             # colormap/palette tag
@@ -548,9 +549,9 @@ def test_fp_leak(self) -> None:
         with pytest.raises(OSError):
             os.close(fn)
 
-    def test_multipage(self) -> None:
+    def test_multipage(self, monkeypatch: pytest.MonkeyPatch) -> None:
         # issue #862
-        TiffImagePlugin.READ_LIBTIFF = True
+        monkeypatch.setattr(TiffImagePlugin, "READ_LIBTIFF", True)
         with Image.open("Tests/images/multipage.tiff") as im:
             # file is a multipage tiff,  10x10 green, 10x10 red, 20x20 blue
 
@@ -569,11 +570,9 @@ def test_multipage(self) -> None:
             assert im.size == (20, 20)
             assert im.convert("RGB").getpixel((0, 0)) == (0, 0, 255)
 
-        TiffImagePlugin.READ_LIBTIFF = False
-
-    def test_multipage_nframes(self) -> None:
+    def test_multipage_nframes(self, monkeypatch: pytest.MonkeyPatch) -> None:
         # issue #862
-        TiffImagePlugin.READ_LIBTIFF = True
+        monkeypatch.setattr(TiffImagePlugin, "READ_LIBTIFF", True)
         with Image.open("Tests/images/multipage.tiff") as im:
             frames = im.n_frames
             assert frames == 3
@@ -582,35 +581,30 @@ def test_multipage_nframes(self) -> None:
                 # Should not raise ValueError: I/O operation on closed file
                 im.load()
 
-        TiffImagePlugin.READ_LIBTIFF = False
-
-    def test_multipage_seek_backwards(self) -> None:
-        TiffImagePlugin.READ_LIBTIFF = True
+    def test_multipage_seek_backwards(self, monkeypatch: pytest.MonkeyPatch) -> None:
+        monkeypatch.setattr(TiffImagePlugin, "READ_LIBTIFF", True)
         with Image.open("Tests/images/multipage.tiff") as im:
             im.seek(1)
             im.load()
 
             im.seek(0)
             assert im.convert("RGB").getpixel((0, 0)) == (0, 128, 0)
 
-        TiffImagePlugin.READ_LIBTIFF = False
-
-    def test__next(self) -> None:
-        TiffImagePlugin.READ_LIBTIFF = True
+    def test__next(self, monkeypatch: pytest.MonkeyPatch) -> None:
+        monkeypatch.setattr(TiffImagePlugin, "READ_LIBTIFF", True)
         with Image.open("Tests/images/hopper.tif") as im:
             assert not im.tag.next
             im.load()
             assert not im.tag.next
 
-    def test_4bit(self) -> None:
+    def test_4bit(self, monkeypatch: pytest.MonkeyPatch) -> None:
         # Arrange
         test_file = "Tests/images/hopper_gray_4bpp.tif"
         original = hopper("L")
 
         # Act
-        TiffImagePlugin.READ_LIBTIFF = True
+        monkeypatch.setattr(TiffImagePlugin, "READ_LIBTIFF", True)
         with Image.open(test_file) as im:
-            TiffImagePlugin.READ_LIBTIFF = False
 
             # Assert
             assert im.size == (128, 128)
@@ -650,12 +644,12 @@ def test_gray_semibyte_per_pixel(self) -> None:
                     assert im2.mode == "L"
                     assert_image_equal(im, im2)
 
-    def test_save_bytesio(self) -> None:
+    def test_save_bytesio(self, monkeypatch: pytest.MonkeyPatch) -> None:
         # PR 1011
         # Test TIFF saving to io.BytesIO() object.
 
-        TiffImagePlugin.WRITE_LIBTIFF = True
-        TiffImagePlugin.READ_LIBTIFF = True
+        monkeypatch.setattr(TiffImagePlugin, "WRITE_LIBTIFF", True)
+        monkeypatch.setattr(TiffImagePlugin, "READ_LIBTIFF", True)
 
         # Generate test image
         pilim = hopper()
@@ -672,9 +666,6 @@ def save_bytesio(compression: str | None = None) -> None:
         save_bytesio("packbits")
         save_bytesio("tiff_lzw")
 
-        TiffImagePlugin.WRITE_LIBTIFF = False
-        TiffImagePlugin.READ_LIBTIFF = False
-
     def test_save_ycbcr(self, tmp_path: Path) -> None:
         im = hopper("YCbCr")
         outfile = str(tmp_path / "temp.tif")
@@ -694,15 +685,16 @@ def test_exif_ifd(self, tmp_path: Path) -> None:
             if Image.core.libtiff_support_custom_tags:
                 assert reloaded.tag_v2[34665] == 125456
 
-    def test_crashing_metadata(self, tmp_path: Path) -> None:
+    def test_crashing_metadata(
+        self, monkeypatch: pytest.MonkeyPatch, tmp_path: Path
+    ) -> None:
         # issue 1597
         with Image.open("Tests/images/rdf.tif") as im:
             out = str(tmp_path / "temp.tif")
 
-            TiffImagePlugin.WRITE_LIBTIFF = True
+            monkeypatch.setattr(TiffImagePlugin, "WRITE_LIBTIFF", True)
             # this shouldn't crash
             im.save(out, format="TIFF")
-        TiffImagePlugin.WRITE_LIBTIFF = False
 
     def test_page_number_x_0(self, tmp_path: Path) -> None:
         # Issue 973
@@ -733,20 +725,19 @@ def test_fd_duplication(self, tmp_path: Path) -> None:
         # Should not raise PermissionError.
         os.remove(tmpfile)
 
-    def test_read_icc(self) -> None:
+    def test_read_icc(self, monkeypatch: pytest.MonkeyPatch) -> None:
         with Image.open("Tests/images/hopper.iccprofile.tif") as img:
             icc = img.info.get("icc_profile")
             assert icc is not None
-        TiffImagePlugin.READ_LIBTIFF = True
+        monkeypatch.setattr(TiffImagePlugin, "READ_LIBTIFF", True)
         with Image.open("Tests/images/hopper.iccprofile.tif") as img:
             icc_libtiff = img.info.get("icc_profile")
             assert icc_libtiff is not None
-        TiffImagePlugin.READ_LIBTIFF = False
         assert icc == icc_libtiff
 
-    def test_write_icc(self, tmp_path: Path) -> None:
+    def test_write_icc(self, monkeypatch: pytest.MonkeyPatch, tmp_path: Path) -> None:
         def check_write(libtiff: bool) -> None:
-            TiffImagePlugin.WRITE_LIBTIFF = libtiff
+            monkeypatch.setattr(TiffImagePlugin, "WRITE_LIBTIFF", libtiff)
 
             with Image.open("Tests/images/hopper.iccprofile.tif") as img:
                 icc_profile = img.info["icc_profile"]
@@ -756,10 +747,9 @@ def check_write(libtiff: bool) -> None:
             with Image.open(out) as reloaded:
                 assert icc_profile == reloaded.info["icc_profile"]
 
-        libtiffs = []
+        libtiffs = [False]
         if Image.core.libtiff_support_custom_tags:
             libtiffs.append(True)
-        libtiffs.append(False)
 
         for libtiff in libtiffs:
             check_write(libtiff)
@@ -840,12 +830,13 @@ def test_sampleformat(self) -> None:
 
             assert_image_equal_tofile(im, "Tests/images/copyleft.png", mode="RGB")
 
-    def test_sampleformat_write(self, tmp_path: Path) -> None:
+    def test_sampleformat_write(
+        self, monkeypatch: pytest.MonkeyPatch, tmp_path: Path
+    ) -> None:
         im = Image.new("F", (1, 1))
         out = str(tmp_path / "temp.tif")
-        TiffImagePlugin.WRITE_LIBTIFF = True
+        monkeypatch.setattr(TiffImagePlugin, "WRITE_LIBTIFF", True)
         im.save(out)
-        TiffImagePlugin.WRITE_LIBTIFF = False
 
         with Image.open(out) as reloaded:
             assert reloaded.mode == "F"
@@ -1091,15 +1082,14 @@ def test_sampleformat_not_corrupted(self) -> None:
         with Image.open(out) as im:
             im.load()
 
-    def test_realloc_overflow(self) -> None:
-        TiffImagePlugin.READ_LIBTIFF = True
+    def test_realloc_overflow(self, monkeypatch: pytest.MonkeyPatch) -> None:
+        monkeypatch.setattr(TiffImagePlugin, "READ_LIBTIFF", True)
         with Image.open("Tests/images/tiff_overflow_rows_per_strip.tif") as im:
             with pytest.raises(OSError) as e:
                 im.load()
 
             # Assert that the error code is IMAGING_CODEC_MEMORY
             assert str(e.value) == "-9"
-        TiffImagePlugin.READ_LIBTIFF = False
 
     @pytest.mark.parametrize("compression", ("tiff_adobe_deflate", "jpeg"))
     def test_save_multistrip(self, compression: str, tmp_path: Path) -> None:

Tests/test_imagesequence.py

@@ -60,10 +60,9 @@ def test_tiff() -> None:
 
 
 @skip_unless_feature("libtiff")
-def test_libtiff() -> None:
-    TiffImagePlugin.READ_LIBTIFF = True
+def test_libtiff(monkeypatch: pytest.MonkeyPatch) -> None:
+    monkeypatch.setattr(TiffImagePlugin, "READ_LIBTIFF", True)
     _test_multipage_tiff()
-    TiffImagePlugin.READ_LIBTIFF = False
 
 
 def test_consecutive() -> None:

Tests/test_tiff_ifdrational.py

@@ -57,14 +57,15 @@ def test_nonetype() -> None:
 @pytest.mark.parametrize(
     "libtiff", (pytest.param(True, marks=skip_unless_feature("libtiff")), False)
 )
-def test_ifd_rational_save(tmp_path: Path, libtiff: bool) -> None:
+def test_ifd_rational_save(
+    monkeypatch: pytest.MonkeyPatch, tmp_path: Path, libtiff: bool
+) -> None:
     im = hopper()
     out = str(tmp_path / "temp.tiff")
     res = IFDRational(301, 1)
 
-    TiffImagePlugin.WRITE_LIBTIFF = libtiff
+    monkeypatch.setattr(TiffImagePlugin, "WRITE_LIBTIFF", libtiff)
     im.save(out, dpi=(res, res), compression="raw")
-    TiffImagePlugin.WRITE_LIBTIFF = False
 
     with Image.open(out) as reloaded:
         assert float(IFDRational(301, 1)) == float(reloaded.tag_v2[282])