add regression test

Author: TomAugspurger

pandas/tests/frame/indexing/test_sparse.py

@@ -49,3 +49,18 @@ def test_locindexer_from_spmatrix(self, spmatrix_t, dtype):
         result = df.loc[itr_idx].dtypes.values
         expected = np.full(cols, SparseDtype(dtype, fill_value=0))
         tm.assert_numpy_array_equal(result, expected)
+
+    def test_reindex(self):
+        # https://github.com/pandas-dev/pandas/issues/35286
+        df = pd.DataFrame(
+            {"A": [0, 1], "B": pd.array([0, 1], dtype=pd.SparseDtype("int64", 0))}
+        )
+        result = df.reindex([0, 2])
+        expected = pd.DataFrame(
+            {
+                "A": [0.0, np.nan],
+                "B": pd.array([0.0, np.nan], dtype=pd.SparseDtype("float64", 0.0)),
+            },
+            index=[0, 2],
+        )
+        tm.assert_frame_equal(result, expected)