Python多重继承单元测试 -

Question

我试图了解使用unittest.TestCase类进行多重继承时会发生什么.

MyTest_DoesWork输出我的期望,这既是setUp()和tearDown()被触发.这不会发生MyTest_DoesNotWork.为什么会这样？任何线索？

import unittest

class MyClassTest1(object):
    def setUp(self):
        print 'Setting up', self.__class__
    def test_a1(self):
        print "Running test_a1 for class", self.__class__
    def test_a2(self):
        print "Running test_a2 for class", self.__class__
    def tearDown(self):
        print 'Tearing down', self.__class__

class MyClassTest2(object):
    def setUp(self):
        print 'Setting up', self.__class__
    def test_b1(self):
        print "Running test_b1 for class", self.__class__
    def test_b2(self):
        print "Running test_b2 for class", self.__class__
    def tearDown(self):
        print 'Tearing down', self.__class__

class MyTest_DoesNotWork(unittest.TestCase, MyClassTest1, MyClassTest2):
    """
    Output:
    Running test_a1 for class <class '__main__.MyTest_DoesNotWork'>
    .Running test_a2 for class <class '__main__.MyTest_DoesNotWork'>
    .Running test_b1 for class <class '__main__.MyTest_DoesNotWork'>
    .Running test_b2 for class <class '__main__.MyTest_DoesNotWork'>
    """
    pass

class MyTest_DoesWork(MyClassTest1, MyClassTest2, unittest.TestCase):
    """
    Output:
    Setting up <class '__main__.MyTest_DoesWork'>
    Running test_a1 for class <class '__main__.MyTest_DoesWork'>
    Tearing down <class '__main__.MyTest_DoesWork'>
    .Setting up <class '__main__.MyTest_DoesWork'>
    Running test_a2 for class <class '__main__.MyTest_DoesWork'>
    Tearing down <class '__main__.MyTest_DoesWork'>
    .Setting up <class '__main__.MyTest_DoesWork'>
    Running test_b1 for class <class '__main__.MyTest_DoesWork'>
    Tearing down <class '__main__.MyTest_DoesWork'>
    .Setting up <class '__main__.MyTest_DoesWork'>
    Running test_b2 for class <class '__main__.MyTest_DoesWork'>
    Tearing down <class '__main__.MyTest_DoesWork'>
    """
    pass

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

Answer 1

Python 的方法解析顺序导致了这种情况。对于您的继承结构，它按照您声明父类的顺序从左到右解析。

因此，对于MyTest_DoesNotWork，python 将unittest.TestCase执行setUpand的实现tearDown，它们不执行任何操作。因为unittest.TestCase.setUp不是为了协作和调用其他超类setUp方法而编写的，它只是停在那里并且没有打印任何内容。

使用MyTest_DoesWork，python 将改为MyClassTest1首先解析。就像unittest.TestCase，您还没有编写setUp和tearDown方法来协作调用超类方法。所以它停在那里，从不调用MyClassTest2方法。所以我猜即使这实际上也没有像你预期的那样工作。更改您的MyClassTest1 setUp和tearDown方法以打印出“MyClassTest1”而不是，self.class您将看到它一直被调用。 MyClassTest2 setUp并且tearDown永远不会被调用。