fix: Raise an error when CrossValidationReport fails before at least one estimator is fitted

skore/src/skore/sklearn/_cross_validation/report.py

@@ -222,6 +222,11 @@ def _fit_estimator_reports(self) -> list[EstimatorReport]:
                     border_style="cyan",
                 )
             )
+            if len(estimator_reports) == 0:
+                raise RuntimeError(
+                    "Cross-validation failed: no estimators were successfully fitted. "
+                    "Please check your data, estimator, or cross-validation setup."
+                ) from None
 
         return estimator_reports
 

skore/tests/unit/sklearn/test_cross_validation.py

@@ -988,3 +988,21 @@ def test_cross_validation_timings(
         "Predict time test",
     ]
     assert timings.columns.tolist() == expected_columns
+
+
+class BrokenEstimator(BaseEstimator, ClassifierMixin):
+    def fit(self, X, y):
+        raise ValueError("Intentional failure for testing")
+
+    def predict(self, X):
+        return [0] * len(X)
+
+
+def test_cross_validation_report_with_zero_estimators():
+    X, y = make_classification(n_samples=100, n_features=10, random_state=42)
+
+    with pytest.raises(
+        RuntimeError,
+        match="Cross-validation failed: no estimators were successfully fitted",
+    ):
+        CrossValidationReport(BrokenEstimator(), X, y)