PyCharm 2018 中测试失败的两个回溯

Question

我在site_tests.py 文件中有简单的测试：

import unittest


class SiteTests(unittest.TestCase):

    def test(self):
        self.assertEqual('a', 'b')

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

当我使用默认 PyCharm 配置运行“Unittest in test_site.py”时，我得到：

Testing started at 23:45 ...
C:\Users\testSite\AppData\Local\Programs\Python\Python36-32\python.exe "C:\Program Files\JetBrains\PyCharm Community Edition 2018.1.3\helpers\pycharm\_jb_unittest_runner.py" --path C:/testSiteDemoTests/site_tests.py
Launching unittests with arguments python -m unittest C:/testSiteDemoTests/site_tests.py in C:\testSiteDemoTests


b != a

Expected :a
Actual   :b
 <Click to see difference>

Traceback (most recent call last):
  File "C:\Program Files\JetBrains\PyCharm Community Edition 2018.1.3\helpers\pycharm\teamcity\diff_tools.py", line 32, in _patched_equals
    old(self, first, second, msg)
  File "C:\Users\testSite\AppData\Local\Programs\Python\Python36-32\lib\unittest\case.py", line 829, in assertEqual
    assertion_func(first, second, msg=msg)
  File "C:\Users\testSite\AppData\Local\Programs\Python\Python36-32\lib\unittest\case.py", line 1202, in assertMultiLineEqual
    self.fail(self._formatMessage(msg, standardMsg))
  File "C:\Users\testSite\AppData\Local\Programs\Python\Python36-32\lib\unittest\case.py", line 670, in fail
    raise self.failureException(msg)
AssertionError: 'a' != 'b'
- a
+ b


During handling of the above exception, another exception occurred:

Traceback (most recent call last):
  File "C:\Users\testSite\AppData\Local\Programs\Python\Python36-32\lib\unittest\case.py", line 59, in testPartExecutor
    yield
  File "C:\Users\testSite\AppData\Local\Programs\Python\Python36-32\lib\unittest\case.py", line 605, in run
    testMethod()
  File "C:\testSiteDemoTests\site_tests.py", line 7, in test
    self.assertEqual('a', 'b')



Ran 1 test in 0.000s

FAILED (failures=1)

Process finished with exit code 1

最后一部分非常有趣，因为没有_jb_unittest_runner.py所以运行这个文件C:\testSite>python lost_hat_tests.py 输出没问题：

F
======================================================================
FAIL: test (__main__.SiteTests)
----------------------------------------------------------------------
Traceback (most recent call last):
  File "lost_hat_tests.py", line 7, in test
    self.assertEqual('a', 'b')
AssertionError: 'a' != 'b'
- a
+ b


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

FAILED (failures=1)

是否有简单的答案为什么第二条消息出现在 PyCharm 运行器中？

我还在控制台中使用 _jb_unittest_runner.py 运行测试 - 嗯，两个 testSuites - 很有趣

C:\testSiteDemoTests>python "C:\Program Files\JetBrains\PyCharm Community Edition 2018.1.3\helpers\pycharm\_jb_unittest_runner.py" --path C:/testSiteDemoTests/site_tests.py
##teamcity[enteredTheMatrix timestamp='2018-05-20T23:59:59.931']
Launching unittests with arguments python -m unittest C:/testSiteDemoTests/site_tests.py in C:\testSiteDemoTests

##teamcity[testCount timestamp='2018-05-20T23:59:59.946' count='1']
##teamcity[testSuiteStarted timestamp='2018-05-20T23:59:59.946' locationHint='python<C:\testSiteDemoTests>://site_tests' name='site_tests' nodeId='1' parentNodeId='0']
##teamcity[testSuiteStarted timestamp='2018-05-20T23:59:59.946' locationHint='python<C:\testSiteDemoTests>://site_tests.SiteTests' name='SiteTests' nodeId='2' parentNodeId='1']
##teamcity[testStarted timestamp='2018-05-20T23:59:59.962' captureStandardOutput='true' locationHint='python<C:\testSiteDemoTests>://site_tests.SiteTests.test' name='test' nodeId='3' parentNodeId='2']
##teamcity[testFailed timestamp='2018-05-20T23:59:59.977' actual='b' details='Traceback (most recent call last):|n  File "C:\Program Files\JetBrains\PyCharm Community Edition 2018.1.3\helpers\pycharm\teamcity\diff_tools.py", line 32, in _patched_equals|n    old(
self, first, second, msg)|n  File "C:\Users\testSite\AppData\Local\Programs\Python\Python36-32\lib\unittest\case.py", line 829, in assertEqual|n    assertion_func(first, second, msg=msg)|n  File "C:\Users\testSite\AppData\Local\Programs\Python\Python36-32\
lib\unittest\case.py", line 1202, in assertMultiLineEqual|n    self.fail(self._formatMessage(msg, standardMsg))|n  File "C:\Users\testSite\AppData\Local\Programs\Python\Python36-32\lib\unittest\case.py", line 670, in fail|n    raise self.failureException(msg)
|nAssertionError: |'a|' != |'b|'|n- a|n+ b|n|n|nDuring handling of the above exception, another exception occurred:|n|nTraceback (most recent call last):|n  File "C:\Users\testSite\AppData\Local\Programs\Python\Python36-32\lib\unittest\case.py", line 59, in t
estPartExecutor|n    yield|n  File "C:\Users\testSite\AppData\Local\Programs\Python\Python36-32\lib\unittest\case.py", line 605, in run|n    testMethod()|n  File "C:\testSiteDemoTests\site_tests.py", line 7, in test|n    self.assertEqual(|'a|', |'b|')|n' e
xpected='a' locationHint='python<C:\testSiteDemoTests>://site_tests.SiteTests.test' message='|nb != a|n' name='test' nodeId='3' parentNodeId='2' type='comparisonFailure']
##teamcity[testFinished timestamp='2018-05-20T23:59:59.977' duration='30' locationHint='python<C:\testSiteDemoTests>://site_tests.SiteTests.test' name='test' nodeId='3' parentNodeId='2']


Ran 1 test in 0.031s

FAILED (failures=1)
##teamcity[testSuiteFinished timestamp='2018-05-20T23:59:59.977' locationHint='python<C:\testSiteDemoTests>://site_tests.SiteTests' name='SiteTests' nodeId='2' parentNodeId='1']
##teamcity[testSuiteFinished timestamp='2018-05-20T23:59:59.977' locationHint='python<C:\testSiteDemoTests>://site_tests' name='site_tests' nodeId='1' parentNodeId='0']

Answer 1

This message shows up 在 Python 3 中的异常格式中，如果 another exception was raised in an exception handler or finally clause 是第一个：

如果在异常处理程序或finally 子句中引发异常，类似的机制会隐式起作用：然后将先前的异常作为新异常的__context__ 属性附加

在 PyCharm 中的测试上设置断点，然后进一步进入机器显示第二个异常被抛出的位置。 _jb_unittest_runner 修补了unittest 中的断言方法：

PyCharm Community Edition\helpers\pycharm\_jb_unittest_runner.py:

from teamcity import unittestpy

PyCharm Community Edition\helpers\pycharm\teamcity\unittestpy.py:

def run(self, test):
    <...>
    patch_unittest_diff(subtest_filter)
    <...>

PyCharm Community Edition\helpers\pycharm\teamcity\diff_tools.py:

def patch_unittest_diff(<...>):

    old = unittest.TestCase.assertEqual

    def _patched_equals(self, first, second, msg=None):
        try:
            old(self, first, second, msg)
            return
        except AssertionError as native_error:
            if not test_filter or test_filter(self):
                error = EqualsAssertionError(first, second, msg)
                if error.can_be_serialized():
                    raise error
            raise native_error

    unittest.TestCase.assertEqual = _patched_equals