scikit-learn
diff --git a/‎sklearn/utils/estimator_checks.py
Lines changed: 36 additions & 14 deletions b/‎sklearn/utils/estimator_checks.py
Lines changed: 36 additions & 14 deletions
diff --git a/‎sklearn/utils/tests/test_estimator_checks.py
Lines changed: 1 addition & 5 deletions b/‎sklearn/utils/tests/test_estimator_checks.py
Lines changed: 1 addition & 5 deletions
@@ -82,10 +82,17 @@
 
 
 def _yield_api_checks(estimator):
+    tags = get_tags(estimator)
+    yield check_estimator_cloneable
     yield check_estimator_repr
     yield check_no_attributes_set_in_init
     yield check_fit_score_takes_y
     yield check_estimators_overwrite_params
+    yield check_dont_overwrite_parameters
+    yield check_estimators_fit_returns_self
+    yield check_readonly_memmap_input
+    if tags.requires_fit:
+        yield check_estimators_unfitted
     yield check_do_not_raise_errors_in_init_or_set_params
 
 
@@ -104,8 +111,6 @@ def _yield_checks(estimator):
             yield check_sample_weights_not_overwritten
             yield partial(check_sample_weights_invariance, kind="ones")
             yield partial(check_sample_weights_invariance, kind="zeros")
-    yield check_estimators_fit_returns_self
-    yield partial(check_estimators_fit_returns_self, readonly_memmap=True)
 
     # Check that all estimator yield informative messages when
     # trained on empty datasets
@@ -173,8 +178,6 @@ def _yield_classifier_checks(classifier):
         yield check_supervised_y_no_nan
         if tags.target_tags.single_output:
             yield check_supervised_y_2d
-    if tags.requires_fit:
-        yield check_estimators_unfitted
     if "class_weight" in classifier.get_params().keys():
         yield check_class_weight_classifiers
 
@@ -247,8 +250,6 @@ def _yield_regressor_checks(regressor):
     if name != "CCA":
         # check that the regressor handles int input
         yield check_regressors_int
-    if tags.requires_fit:
-        yield check_estimators_unfitted
     yield check_non_transformer_estimators_n_iter
 
 
@@ -311,9 +312,6 @@ def _yield_outliers_checks(estimator):
         yield partial(check_outliers_train, readonly_memmap=True)
         # test outlier detectors can handle non-array data
         yield check_classifier_data_not_an_array
-        # test if NotFittedError is raised
-        if get_tags(estimator).requires_fit:
-            yield check_estimators_unfitted
     yield check_non_transformer_estimators_n_iter
 
 
@@ -381,7 +379,6 @@ def _yield_all_checks(estimator, legacy: bool):
     yield check_get_params_invariance
     yield check_set_params
     yield check_dict_unchanged
-    yield check_dont_overwrite_parameters
     yield check_fit_idempotent
     yield check_fit_check_is_fitted
     if not tags.no_validation:
@@ -2724,18 +2721,34 @@ def check_get_feature_names_out_error(name, estimator_orig):
 
 
 @ignore_warnings(category=FutureWarning)
-def check_estimators_fit_returns_self(name, estimator_orig, readonly_memmap=False):
+def check_estimators_fit_returns_self(name, estimator_orig):
     """Check if self is returned when calling fit."""
     X, y = make_blobs(random_state=0, n_samples=21)
     X = _enforce_estimator_tags_X(estimator_orig, X)
 
     estimator = clone(estimator_orig)
     y = _enforce_estimator_tags_y(estimator, y)
 
-    if readonly_memmap:
-        X, y = create_memmap_backed_data([X, y])
+    set_random_state(estimator)
+    assert estimator.fit(X, y) is estimator
+
+
+@ignore_warnings(category=FutureWarning)
+def check_readonly_memmap_input(name, estimator_orig):
+    """Check that the estimator can handle readonly memmap backed data.
+
+    This is particularly needed to support joblib parallelisation.
+    """
+    X, y = make_blobs(random_state=0, n_samples=21)
+    X = _enforce_estimator_tags_X(estimator_orig, X)
+
+    estimator = clone(estimator_orig)
+    y = _enforce_estimator_tags_y(estimator, y)
+
+    X, y = create_memmap_backed_data([X, y])
 
     set_random_state(estimator)
+    # This should not raise an error and should return self
     assert estimator.fit(X, y) is estimator
 
 
@@ -2745,6 +2758,15 @@ def check_estimators_unfitted(name, estimator_orig):
 
     Unfitted estimators should raise a NotFittedError.
     """
+    err_msg = (
+        "Estimator should raise a NotFittedError when calling `{method}` before fit. "
+        "Either call `check_is_fitted(self)` at the beginning of `{method}` or "
+        "set `tags.requires_fit=False` on estimator tags to disable this check.\n"
+        "- `check_is_fitted`: https://scikit-learn.org/dev/modules/generated/sklearn."
+        "utils.validation.check_is_fitted.html\n"
+        "- Estimator Tags: https://scikit-learn.org/dev/developers/develop."
+        "html#estimator-tags"
+    )
     # Common test for Regressors, Classifiers and Outlier detection estimators
     X, y = _regression_dataset()
 
@@ -2756,7 +2778,7 @@ def check_estimators_unfitted(name, estimator_orig):
         "predict_log_proba",
     ):
         if hasattr(estimator, method):
-            with raises(NotFittedError):
+            with raises(NotFittedError, err_msg=err_msg.format(method=method)):
                 getattr(estimator, method)(X)
 
 
 
@@ -753,10 +753,6 @@ def test_check_estimator():
     msg = "object has no attribute 'fit'"
     with raises(AttributeError, match=msg):
         check_estimator(BaseEstimator())
-    # check that fit does input validation
-    msg = "Did not raise"
-    with raises(AssertionError, match=msg):
-        check_estimator(BaseBadClassifier())
 
     # does error on binary_only untagged estimator
     msg = "Only 2 classes are supported"
@@ -836,7 +832,7 @@ def test_check_estimator_clones():
 def test_check_estimators_unfitted():
     # check that a ValueError/AttributeError is raised when calling predict
     # on an unfitted estimator
-    msg = "Did not raise"
+    msg = "Estimator should raise a NotFittedError when calling"
     with raises(AssertionError, match=msg):
         check_estimators_unfitted("estimator", NoSparseClassifier())