unittest使用过程中sys.exit(not self.result.wasSuccessful())

起因：

在运行下面的unittest过程中出现了个Traceback:

被测试脚本：

# splitter.py
def split(line, types=None, delimiter=None):
    """Splits a line of test and optionally performs type conversion.
    For example:

    >>> split('GOOD 100 490.50')
    ['GOOD', '100', '490.50']
    >>> split('GOOD 100 490.50', [str, int, float])
    ['GOOD', 100, 490.50]
    >>>
    By default, splitting is perfomed on whitespace, but a different delimiter
    can be selected with the delimiter keyword argument:

    >>> split('GOOD, 100, 490.50', delimiter=',')
    ['GOOOD', '100', '490.50']
    >>>
    """

    fields = line.split(delimiter)
    if types:
        fields = [ty(val) for ty, val in zip(types, fields)]
    return fields

if __name__ == '__main__':
    # test myself
    import doctest
    doctest.testmod()

 测试脚本：

# testsplitter.py
import splitter
import unittest

# unit test
class TestSplitFunction(unittest.TestCase):
    def setUp(self):
        pass
    def tearDown(self):
        pass
    def testsimplestring(self):
        r = splitter.split('GOOD 100 490.50')
        self.assertEqual(r, ['GOOD', '100', '490.50'])
    def testypeconvert(self):
        r = splitter.split('GOOD 100 490.50', [str, int, float])
        self.assertAlmostEqual(r, ['GOOD', 100, 490.50])
    def testdelimiter(self):
        r = splitter.split('GOOD,100,490.50', delimiter=',')
        self.assertEqual(r, ['GOOD', '100', '490.50'])

# Run unit test
if __name__ == '__main__':
    unittest.main()

 结果：

...
----------------------------------------------------------------------
Ran 3 tests in 0.011s

OK
Traceback (most recent call last):
  File "C:UsersAdministratorDesktopPython Scripts	estsplitter - 副本.py", line 23, in <module>
    unittest.main()
  File "D:Python33libunittestmain.py", line 125, in __init__
    self.runTests()
  File "D:Python33libunittestmain.py", line 267, in runTests
    sys.exit(not self.result.wasSuccessful())
SystemExit: False
>>> ================================ RESTART ================================
>>> 
...
----------------------------------------------------------------------
Ran 3 tests in 0.011s

OK
Traceback (most recent call last):
  File "C:UsersAdministratorDesktopPython Scripts	estsplitter - 副本.py", line 23, in <module>
    unittest.main()
  File "D:Python33libunittestmain.py", line 125, in __init__
    self.runTests()
  File "D:Python33libunittestmain.py", line 267, in runTests
    sys.exit(not self.result.wasSuccessful())
SystemExit: False

 从结果看，所有测试用例是都通过的，但是出现了Traceback，SystemExit: False.

分析：

查找到的链接： http://bugs.python.org/issue2821

这是一个IDLE问题

IDLE catches the SystemExit function raised by TestProgram().runTests()
and prints the traceback. Not a bug in unittest.

因为unittest.main()函数会调用sys.exit()来结束函数进程。使用的参数就是not self.result.wasSuccessful()

进一步分析：

那如果是assert过程中出现fail，会是什么样？

修改测试脚本：

# testsplitter.py
import splitter
import unittest

# unit test
class TestSplitFunction(unittest.TestCase):
    def setUp(self):
        pass
    def tearDown(self):
        pass
    def testsimplestring(self):
        r = splitter.split('GOOD 100 490.50')
        self.assertEqual(r, ['GOOD', '100', '490.50'])
    def testypeconvert(self):
        r = splitter.split('GOOD 100 490.50', [str, int, float])
        self.assertAlmostEqual(r, ['GOOD', 10, 490.50])  # Modify this line
    def testdelimiter(self):
        r = splitter.split('GOOD,100,490.50', delimiter=',')
        self.assertEqual(r, ['GOOD', '100', '490.50'])

# Run unit test
if __name__ == '__main__':
    unittest.main()

 运行结果：

..E
======================================================================
ERROR: testypeconvert (__main__.TestSplitFunction)
----------------------------------------------------------------------
Traceback (most recent call last):
  File "C:UsersAdministratorDesktopPython Scripts	estsplitter - 副本.py", line 16, in testypeconvert
    self.assertAlmostEqual(r, ['GOOD', 10, 490.50])
  File "D:Python33libunittestcase.py", line 683, in assertAlmostEqual
    if round(abs(second-first), places) == 0:
TypeError: unsupported operand type(s) for -: 'list' and 'list'

----------------------------------------------------------------------
Ran 3 tests in 0.077s

FAILED (errors=1)
Traceback (most recent call last):
  File "C:UsersAdministratorDesktopPython Scripts	estsplitter - 副本.py", line 23, in <module>
    unittest.main()
  File "D:Python33libunittestmain.py", line 125, in __init__
    self.runTests()
  File "D:Python33libunittestmain.py", line 267, in runTests
    sys.exit(not self.result.wasSuccessful())
SystemExit: True

分析：

unittest里面的assert和一般的assert是不一样的，即使fail了，其实还是会继续执行其他的测试用例，不会立即跳出函数。最后跳出函数还是调用sys.exit(),只不过这个时候的参数就是True了。

类似sys.exit(1) - 表示非正常退出。在unittest里面表示有测试用例失败。

sys.exist(0) - 正常退出。在unittest里面表示测试用例均通过。