TST: Increases coverage

thomasjpfan · thomasjpfan · commit b6db9ca0d85a · 2018-08-23T12:41:11.000-04:00
diff --git a/sklearn/compose/tests/test_column_transformer.py b/sklearn/compose/tests/test_column_transformer.py
@@ -363,6 +363,26 @@ def test_column_transformer_sparse_array():
         assert_allclose_dense_sparse(
             ct.inverse_transform(X_res_both), X_sparse)
 
+    class TransSparseToArray(BaseEstimator):
+        def fit(self, X, y=None):
+            return self
+
+        def transform(self, X, y=None):
+            return X.toarray()
+
+        def inverse_transform(self, X):
+            return sparse.csr_matrix(X)
+            
+    X_res_both = X_sparse.toarray()
+    for col in [[0, 1], slice(0, 2)]:
+        ct = ColumnTransformer([('trans', TransSparseToArray(), col)],
+                               sparse_threshold=0.8)
+        assert_allclose_dense_sparse(ct.fit_transform(X_sparse), X_res_both)
+        assert_allclose_dense_sparse(ct.fit(X_sparse).transform(X_sparse),
+                                     X_res_both)
+        assert_allclose_dense_sparse(
+            ct.inverse_transform(X_res_both), X_sparse)
+
 
 def test_column_transformer_sparse_stacking():
     X_array = np.array([[0, 1, 2], [2, 4, 6]]).T
