test: Reproduce issue

skore/tests/unit/sklearn/test_estimator.py

@@ -925,3 +925,28 @@ def test_estimator_report_get_X_y_and_data_source_hash(data_source):
         assert X is X_test
         assert y is y_test
         assert data_source_hash == joblib.hash((X_test, y_test))
+
+
+def test_estimator_has_side_effects():
+    """Re-fitting the estimator outside the EstimatorReport
+    should not have an effect on the EstimatorReport's internal estimator"""
+    X, y = make_classification(n_classes=2, random_state=42)
+    X_train, X_test, y_train, y_test = train_test_split(X, y, random_state=42)
+    X_train2, _, y_train2, _ = train_test_split(X, y, random_state=420)
+
+    estimator = LogisticRegression().fit(X_train, y_train)
+    report = EstimatorReport(
+        estimator,
+        X_train=X_train,
+        X_test=X_test,
+        y_train=y_train,
+        y_test=y_test,
+    )
+
+    predictions_before = report.estimator.predict_proba(X_test)
+
+    estimator.fit(X_train2, y_train2)
+
+    predictions_after = report.estimator.predict_proba(X_test)
+
+    np.testing.assert_array_equal(predictions_before, predictions_after)