test for retaining sklearn config

skbase/tests/test_base.py

@@ -1123,8 +1123,8 @@ def test_clone_class_rather_than_instance_raises_error(
     not _check_soft_dependencies("scikit-learn", severity="none"),
     reason="skip test if sklearn is not available",
 )  # sklearn is part of the dev dependency set, test should be executed with that
-def test_clone_sklearn_composite(fixture_class_parent: Type[Parent]):
-    """Test clone with keyword parameter set to None."""
+def test_clone_sklearn_composite():
+    """Test clone with a composite of sklearn and skbase."""
     from sklearn.ensemble import GradientBoostingRegressor
 
     sklearn_obj = GradientBoostingRegressor(random_state=5, learning_rate=0.02)
@@ -1134,6 +1134,23 @@ def test_clone_sklearn_composite(fixture_class_parent: Type[Parent]):
     assert composite_set.get_params()["a__random_state"] == 42
 
 
+@pytest.mark.skipif(
+    not _check_soft_dependencies("scikit-learn", severity="none"),
+    reason="skip test if sklearn is not available",
+)  # sklearn is part of the dev dependency set, test should be executed with that
+def test_clone_sklearn_composite_retains_config():
+    """Test that clone retains sklearn config if inside skbase composite."""
+    from sklearn.preprocessing import StandardScaler
+
+    sklearn_obj_w_config = StandardScaler().set_output(transform="pandas")
+
+    composite = ResetTester(a=sklearn_obj_w_config)
+    composite_clone = composite.clone()
+
+    assert hasattr(composite_clone, "_sklearn_output_config")
+    assert composite_clone._sklearn_output_config.get("transform", None) == "pandas"
+
+
 # Tests of BaseObject pretty printing representation inspired by sklearn
 def test_baseobject_repr(
     fixture_class_parent: Type[Parent],