TST: to_json keeps column info with empty dataframe (#7445)

Author: mroeschke

pandas/io/tests/json/test_pandas.py

@@ -1011,6 +1011,11 @@ def roundtrip(s, encoding='latin-1'):
         for s in examples:
             roundtrip(s)
 
+    def test_to_json_column_with_empty_dataframe(self):
+        # GH 7445
+        result = pd.DataFrame({'test': []}, index=[]).to_json(orient='columns')
+        expected = '{"test":{}}'
+        tm.assert_equal(result, expected)
 
 if __name__ == '__main__':
     nose.runmodule(argv=[__file__, '-vvs', '-x', '--pdb',