fix/adjust test_disable_plugin_autoload

testing/test_config.py

@@ -665,6 +665,13 @@ class Distribution:
     class PseudoPlugin:
         x = 42
 
+        attrs_used = []
+
+        def __getattr__(self, name):
+            assert name == "__loader__"
+            self.attrs_used.append(name)
+            return object()
+
     def distributions():
         return (Distribution(),)
 
@@ -674,6 +681,10 @@ def distributions():
     config = testdir.parseconfig(*parse_args)
     has_loaded = config.pluginmanager.get_plugin("mytestplugin") is not None
     assert has_loaded == should_load
+    if should_load:
+        assert PseudoPlugin.attrs_used == ["__loader__"]
+    else:
+        assert PseudoPlugin.attrs_used == []
 
 
 def test_cmdline_processargs_simple(testdir):