Added test case for GH 14334

Author: Jon M. Mease

pandas/tests/test_groupby.py

@@ -442,6 +442,11 @@ def test_grouper_creation_bug(self):
         result = g.sum()
         assert_frame_equal(result, expected)
 
+        # GH14334
+        g = df.groupby([pd.Grouper(key='A')])
+        result = g.sum()
+        assert_frame_equal(result, expected)
+
         # GH8866
         s = Series(np.arange(8, dtype='int64'),
                    index=pd.MultiIndex.from_product(