Added test case to check extension arrays dtype

Author: 5hirish

pandas/tests/groupby/test_grouping.py

@@ -282,6 +282,13 @@ def test_groupby_categorical_index_and_columns(self, observed):
         expected = DataFrame(data=expected_data.T, index=expected_columns)
         assert_frame_equal(result, expected)
 
+    def test_groupby_extension_array(self):
+        df = pd.DataFrame({'Int': pd.Series([1, 2, 3], dtype='Int64'),
+                           'A': [1, 2, 1]})
+        result = df.groupby('A').Int.sum()
+        assert result is not None
+        assert result.dtype.name == 'Int64'
+
     def test_grouper_getting_correct_binner(self):
 
         # GH 10063