Comparing multiline strings in Python unit test

Question

When I compare two Unicode strings in a Python unit test, it gives a good error message indicating which strings and characters are different. However, comparing two 8-bit lines shows two lines without highlighting.

How to get highlight for both Unicode and 8-bit strings?

Here is an example unit test that shows both comparisons:

import unittest

class TestAssertEqual(unittest.TestCase):
    def testString(self):
        a = 'xax\nzzz'
        b = 'xbx\nzzz'
        self.assertEqual(a, b)

    def testUnicode(self):
        a = u'xax\nzzz'
        b = u'xbx\nzzz'
        self.assertEqual(a, b)

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

The results of this test show the difference:

FF
======================================================================
FAIL: testString (__main__.TestAssertEqual)
----------------------------------------------------------------------
Traceback (most recent call last):
  File "/mnt/data/don/workspace/scratch/scratch.py", line 7, in testString
    self.assertEqual(a, b)
AssertionError: 'xax\nzzz' != 'xbx\nzzz'

======================================================================
FAIL: testUnicode (__main__.TestAssertEqual)
----------------------------------------------------------------------
Traceback (most recent call last):
  File "/mnt/data/don/workspace/scratch/scratch.py", line 12, in testUnicode
    self.assertEqual(a, b)
AssertionError: u'xax\nzzz' != u'xbx\nzzz'
- xax
?  ^
+ xbx
?  ^
  zzz

----------------------------------------------------------------------
Ran 2 tests in 0.001s

FAILED (failures=2)

Answer 1

A small copy of the Python source code shows that it TestCaseregisters a bunch of methods for checking equality for different types.

self.addTypeEqualityFunc(dict, 'assertDictEqual')
self.addTypeEqualityFunc(list, 'assertListEqual')
self.addTypeEqualityFunc(tuple, 'assertTupleEqual')
self.addTypeEqualityFunc(set, 'assertSetEqual')
self.addTypeEqualityFunc(frozenset, 'assertSetEqual')
try:
    self.addTypeEqualityFunc(unicode, 'assertMultiLineEqual')
except NameError:
    # No unicode support in this build
    pass

, unicode assertMultiLineEqual(), str . , str , .

8- assertMultiLineEqual() , .

def testString(self):
    a = 'xax\nzzz'
    b = 'xbx\nzzz'
    self.assertMultiLineEqual(a, b)

. setUp(). , . , .

class TestAssertEqual(unittest.TestCase):
    def setUp(self):
        super(TestAssertEqual, self).setUp()
        self.addTypeEqualityFunc(str, self.assertMultiLineEqual)

    def testString(self):
        a = 'xax\nzzz'
        b = 'xbx\nzzz'
        self.assertEqual(a, b)

    def testUnicode(self):
        a = u'xax\nzzz'
        b = u'xbx\nzzz'
        self.assertEqual(a, b)

, .