address PR comment: add assert_frame_equal

Author: litang99

pandas/tests/indexing/test_loc.py

@@ -273,8 +273,9 @@ def test_loc_empty_slice_assignment_with_datetime(self, data):
         mask = [False] * len(data)
         try:
             df = DataFrame(data=data, columns=["A"])
-            df.loc[mask] = df
-            assert True
+            res = df.loc[mask]
+            res = df
+            tm.assert_frame_equal(res, df)
         except Exception:
             pytest.fail("loc empty slice assignment raised Exception unexpectedly!")