PyConUK sprint on improving output from unittest when `assertEqual` finds non-matching values.

NOTES.rst

Unittest documentation improvements

http://www.pyconuk.org/sprints/unit-test-documentation-improvements/

We explored where the "Expected: 1, actual: 2" messages (used to) come from in unittest. We found that this code has already been improved back in 2011. Why were we still getting old output for so long?

Below are links to our findings, plus you can see the test cases we built and tested on various versions of Python.

Key BDFL 'ruling' ----------------

https://mail.python.org/pipermail/python-dev/2010-December/106954.html

... the least bad thing would be to drop any remnants of expected/actual terminology, keep the diffs in the first-second order, and let developers choose whether they put the expected value first or second.

Main issue

• Consistency in unittest assert methods: order of actual, expected: http://bugs.python.org/issue10573

Related issues

• additional unittest type equality methods: https://bugs.python.org/issue2578
• 3.3 unittest document not kept consist with code: https://bugs.python.org/issue11282
• https://bugs.python.org/issue14832
• summary: Issue #10242: backport of more fixes to unittest.TestCase.assertItemsEqual

python_2.6.out

F
======================================================================
FAIL: test_eq_vars (__main__.TestExample)
----------------------------------------------------------------------
Traceback (most recent call last):
  File "test_example.py", line 13, in test_eq_vars
    self.assertEqual(apple, pear)
AssertionError: 1 != {}

----------------------------------------------------------------------
Ran 1 test in 0.001s

FAILED (failures=1)

python_2.7.out

F
======================================================================
FAIL: test_eq_vars (__main__.TestExample)
----------------------------------------------------------------------
Traceback (most recent call last):
  File "test_example.py", line 13, in test_eq_vars
    self.assertEqual(apple, pear)
AssertionError: 1 != {}

----------------------------------------------------------------------
Ran 1 test in 0.000s

FAILED (failures=1)

python_3.4.out

F
======================================================================
FAIL: test_eq_vars (__main__.TestExample)
----------------------------------------------------------------------
Traceback (most recent call last):
  File "test_example.py", line 13, in test_eq_vars
    self.assertEqual(apple, pear)
AssertionError: 1 != {}

----------------------------------------------------------------------
Ran 1 test in 0.000s

FAILED (failures=1)

test_example.py

try:
    import unittest2 as unittest
except ImportError:
    import unittest


class TestExample(unittest.TestCase):

    def test_eq_vars(self):
        apple = 1
        pear = {}

        self.assertEqual(apple, pear)


if __name__ == '__main__':
    unittest.main()