Add test capturing failure. Ref #110.

Author: jaraco

importlib_metadata/tests/fixtures.py

@@ -47,6 +47,15 @@ def tempdir_as_cwd():
             yield tmp
 
 
+@contextlib.contextmanager
+def install_finder(finder):
+    sys.meta_path.append(finder)
+    try:
+        yield
+    finally:
+        sys.meta_path.remove(finder)
+
+
 class Fixtures:
     def setUp(self):
         self.fixtures = ExitStack()
@@ -203,3 +212,8 @@ def build_files(file_defs, prefix=pathlib.Path()):
 def DALS(str):
     "Dedent and left-strip"
     return textwrap.dedent(str).lstrip()
+
+
+class NullFinder:
+    def find_module(self, name):
+        pass

importlib_metadata/tests/test_integration.py

@@ -4,6 +4,7 @@
 
 from . import fixtures
 from .. import version
+from .. import _compat
 
 
 class IntegrationTests(fixtures.DistInfoPkg, unittest.TestCase):
@@ -20,3 +21,20 @@ def is_installed(package_spec):
         assert is_installed('distinfo-pkg==1.0')
         assert is_installed('distinfo-pkg>=1.0,<2.0')
         assert not is_installed('distinfo-pkg<1.0')
+
+
+class FinderTests(fixtures.Fixtures, unittest.TestCase):
+
+    def test_finder_without_module(self):
+        class ModuleFreeFinder(fixtures.NullFinder):
+            """
+            A finder without an __module__ attribute
+            """
+            def __getattribute__(self, name):
+                if name == '__module__':
+                    raise AttributeError(name)
+                return super().__getattribute__(name)
+
+        self.fixtures.enter_context(
+            fixtures.install_finder(ModuleFreeFinder()))
+        _compat.disable_stdlib_finder()