Python：为什么 unittest assertEqual 在这些列表上抛出错误而不是失败？

Question

Python 2.7 和 3.4：为什么test_unexpected_error测试会抛出错误而不是失败？

import unittest

class TestLists(unittest.TestCase):

    def test_unexpected_error(self):

        self.assertEqual([0] * 1000 + [1], [1] + [0] * 1000)

    def test_fails_as_expected(self):

        self.assertEqual([0] * 1000 + [1], [0] * 1000 + [0])

if __name__ == '__main__':

    unittest.main()

错误是：

RuntimeError: maximum recursion depth exceeded while calling a Python object

回溯（删节 - 递归错误是递归错误是递归错误是......）

Traceback (most recent call last):

  File "sotest.py", line 7, in test_unexpected_error

    self.assertEquals([0] * 1000 + [1], [1] + [0] * 1000)

  File "/usr/lib/python2.7/unittest/case.py", line 513, in assertEqual

    assertion_func(first, second, msg=msg)

  File "/usr/lib/python2.7/unittest/case.py", line 743, in assertListEqual

    self.assertSequenceEqual(list1, list2, msg, seq_type=list)

  File "/usr/lib/python2.7/unittest/case.py", line 722, in assertSequenceEqual

    pprint.pformat(seq2).splitlines()))

  File "/usr/lib/python2.7/difflib.py", line 920, in compare

    for line in g:

  File "/usr/lib/python2.7/difflib.py", line 1038, in _fancy_replace

    for line in self._fancy_helper(a, best_i+1, ahi, b, best_j+1, bhi):

  File "/usr/lib/python2.7/difflib.py", line 1051, in _fancy_helper

    for line in g:

  File "/usr/lib/python2.7/difflib.py", line 1038, in _fancy_replace

    for line in self._fancy_helper(a, best_i+1, ahi, b, best_j+1, bhi):

  File "/usr/lib/python2.7/difflib.py", line 1051, in _fancy_helper

    for line in g:

  File "/usr/lib/python2.7/difflib.py", line 1038, in _fancy_replace

    for line in self._fancy_helper(a, best_i+1, ahi, b, best_j+1, bhi):

  File "/usr/lib/python2.7/difflib.py", line 1051, in _fancy_helper

    for line in g:

Answer 1

这看起来是一个已知的错误。如果您不希望单元测试在失败时显示列表之间的差异，您可以执行以下替代测试：self.assertTrue([0] * 1000 + [1] == [1] + [0] * 1000)