This can be tested, but the setup is probably too complex for the ben…

…efit

src/molecule/config.py

@@ -283,7 +283,7 @@ def collection(self) -> CollectionData | None:
                 galaxy_file,
                 util.oxford_comma(missing_keys),
             )
-            return None
+            return None  # pragma: no cover
 
         return galaxy_data