Only use either Pytest or TestBase cache directory, not both

Author: PGijsbers

tests/conftest.py

@@ -286,6 +286,13 @@ def with_server(request):
 
 @pytest.fixture(autouse=True)
 def with_test_cache(test_files_directory, request):
+    # Skip this fixture for TestBase subclasses - they manage their own cache directory
+    # in setUp()/tearDown(). Having both mechanisms fight over the global config
+    # causes race conditions.
+    if request.instance is not None and isinstance(request.instance, TestBase):
+        yield
+        return
+
     if not test_files_directory.exists():
         raise ValueError(
             f"Cannot find test cache dir, expected it to be {test_files_directory!s}!",