MTN: minor refactoring of JCAB including unit testing to achieve 100% coverage

Author: Valentin-Laurent

mapie/regression/regression.py

@@ -720,14 +720,7 @@ def __init__(
             JackknifeAfterBootstrapRegressor._VALID_AGGREGATION_METHODS
         )
 
-        if isinstance(resampling, int):
-            cv = Subsample(n_resamplings=resampling)
-        elif isinstance(resampling, Subsample):
-            cv = resampling
-        else:
-            raise ValueError(
-                "resampling must be an integer or a Subsample instance"
-            )
+        cv = self._check_and_convert_resampling_to_cv(resampling)
 
         self._mapie_regressor = MapieRegressor(
             estimator=estimator,
@@ -901,6 +894,20 @@ def predict(
         )
         return cast_point_predictions_to_ndarray(predictions)
 
+    @staticmethod
+    def _check_and_convert_resampling_to_cv(
+        resampling: Union[int, Subsample]
+    ) -> Subsample:
+        if isinstance(resampling, int):
+            cv = Subsample(n_resamplings=resampling)
+        elif isinstance(resampling, Subsample):
+            cv = resampling
+        else:
+            raise ValueError(
+                "resampling must be an integer or a Subsample instance"
+            )
+        return cv
+
 
 class MapieRegressor(RegressorMixin, BaseEstimator):
     """

tests_v1/test_unit/test_regression.py

@@ -0,0 +1,28 @@
+import pytest
+from mapie.subsample import Subsample
+from mapie.regression import JackknifeAfterBootstrapRegressor
+
+
+class TestCheckAndConvertResamplingToCv:
+    def test_with_integer(self):
+        regressor = JackknifeAfterBootstrapRegressor()
+        cv = regressor._check_and_convert_resampling_to_cv(50)
+
+        assert isinstance(cv, Subsample)
+        assert cv.n_resamplings == 50
+
+    def test_with_subsample(self):
+        custom_subsample = Subsample(n_resamplings=25, random_state=42)
+        regressor = JackknifeAfterBootstrapRegressor()
+        cv = regressor._check_and_convert_resampling_to_cv(custom_subsample)
+
+        assert cv is custom_subsample
+
+    def test_with_invalid_input(self):
+        regressor = JackknifeAfterBootstrapRegressor()
+
+        with pytest.raises(
+            ValueError,
+            match="resampling must be an integer or a Subsample instance"
+        ):
+            regressor._check_and_convert_resampling_to_cv("invalid_input")