improve tests

Author: abast

pandas/tests/io/test_packers.py

@@ -123,10 +123,10 @@ def test_string_io(self):
  result = read_msgpack(s)
  tm.assert_frame_equal(result, df)
 
- df2 = df.astype({0:'category'}).set_index(0)
- s = to_msgpack(None, df)
+ df2 = df.astype({0: 'category'}).set_index(0)
+ s = to_msgpack(None, df2)
  result = read_msgpack(s)
- tm.assert_frame_equal(result, df)
+ tm.assert_frame_equal(result, df2)
 
  with ensure_clean(self.path) as p: