Added test for disabled image plugin

core/src/toga/images.py

@@ -120,6 +120,7 @@ class Image:
         converters = []
 
         for image_plugin in entry_points(group="toga.image_formats"):
+            print(image_plugin)
             converter = importlib.import_module(f"{image_plugin.value}")
             if converter.image_class is not None:
                 converters.append(converter)

core/tests/test_images.py

@@ -4,6 +4,7 @@ import PIL.Image
 import pytest
 
 import toga
+from toga_dummy.plugins import disabled_converter
 from toga_dummy.plugins.image_converter import CustomImage, CustomImageSubclass
 from toga_dummy.utils import assert_action_performed_with
 
@@ -286,6 +287,11 @@ def test_as_format_custom_class(app, ImageClass):
     assert custom_image.size == (144, 72)
 
 
+def test_disabled_image_plugin(app):
+    """Disabled image plugin shouldn't be available."""
+    assert disabled_converter not in toga.Image._converters()
+
+
 # None is same as supplying nothing; also test a random unrecognized class
 @pytest.mark.parametrize("arg", [None, toga.Button])
 def test_as_format_invalid_input(app, arg):

dummy/pyproject.toml

@@ -63,3 +63,4 @@ dependencies = [
 
 [project.entry-points."toga.image_formats"]
 dummy = "toga_dummy.plugins.image_converter"
+disabled = "toga_dummy.plugins.disabled_converter"

dummy/src/toga_dummy/plugins/disabled_converter.py

@@ -0,0 +1,4 @@
+# With image_class set to None, this shouldn't be added to the list of available
+# converters. This simulates what the PIL plugin does if PIL isn't installed.
+
+image_class = None