TST: Add test on DataFrame columns auto-completion

pandas/tests/frame/test_api.py

@@ -128,6 +128,20 @@ def test_column_contains_typeerror(self):
         except TypeError:
             pass
 
+    def test_tab_completion(self):
+        # DataFrame whose columns are identifiers shall have them in __dir__.
+        df = pd.DataFrame([list('abcd'), list('efgh')], columns=list('ABCD'))
+        assert 'A' in dir(df)
+        assert isinstance(df.__getitem__('A'), pd.Series)
+
+        # DataFrame whose first-level columns are identifiers shall have
+        # them in __dir__.
+        df = pd.DataFrame(
+            [list('abcd'), list('efgh')],
+            columns=pd.MultiIndex.from_tuples(list(zip('ABCD', 'EFGH'))))
+        assert 'A' in dir(df)
+        assert isinstance(df.__getitem__('A'), pd.DataFrame)
+
     def test_not_hashable(self):
         df = self.klass([1])
         pytest.raises(TypeError, hash, df)