在Python中进行单元测试时，如果断言失败，如何将自定义消息与默认消息一起显示？

Question

考虑以下示例：

import unittest

class MessageExampleTest(unittest.TestCase):
    def test_with_default_message(self):
        self.assertEqual('apples', 'oranges')

    def test_with_custom_message(self):
        self.assertEqual('apples', 'oranges', 'You should not compare apples and oranges.')

输出：

======================================================================
FAIL: test_with_default_message (assert_message.MessageExampleTest)
----------------------------------------------------------------------
Traceback (most recent call last):
  ...
    self.assertEqual('apples', 'oranges')
AssertionError: 'apples' != 'oranges'

======================================================================
FAIL: test_with_custom_message (assert_message.MessageExampleTest)
----------------------------------------------------------------------
Traceback (most recent call last):
  ...
    self.assertEqual('apples', 'oranges', 'You should not compare apples and oranges.')
AssertionError: You should not compare apples and oranges.


----------------------------------------------------------------------

在第二种情况下，我希望看到的是：

AssertionError: 'apples' != 'oranges'; You should not compare apples and oranges.

Answer 1

从Python 2.7开始，unittest现在提供了longMessage属性来执行此操作。

在Python 2.7中：

import unittest

class MessageExampleTest(unittest.TestCase):
    def setUp(self):
        self.longMessage = True

    def test_with_custom_message(self):
        self.assertEqual('apples', 'oranges', 'You should not compare apples and oranges.')

输出：

======================================================================
FAIL: test_with_custom_message (assert_message.MessageExampleTest)
----------------------------------------------------------------------
Traceback (most recent call last):
  ...
    self.assertEqual('apples', 'oranges', 'You should not compare apples and oranges.')
AssertionError: 'apples' != 'oranges' : You should not compare apples and oranges.

======================================================================