Python unittest 模块中 unittest.main() 的含义

问题描述

我试图在 Python 中学习单元测试，特别是 unittest 模块.

I was trying to learn unit testing in Python, specifically the unittest module.

考虑以下几行:

import unittest

class abc(unittest.TestCase):
    def xyz():
      ...

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

由于调用了 unittest.main()，我可以看到我所有的测试用例都在运行.

I could see all my test cases running because of the call to unittest.main().

我只是想知道这个调用是如何让所有测试用例运行的.

I was just curious to know how this call is making all the test cases run.

我知道，由于我为每个测试类继承了 unittest.TestCase，它正在发挥所有作用.有什么见解吗?

I know since I'm inheriting from unittest.TestCase for every test class, it is doing all the magic. Any insights?

推荐答案

main 与 unittest 关联实际上是 TestProgram 的一个实例，它在实例化后运行所有测试.

main associated with unittest is actually an instance of TestProgram which, when instantiated, runs all your tests.

以下是从 unittest 源中复制的相关代码">http://pythonhosted.org/gchecky/unittest-pysrc.html:

Below is the relevant code copied from the unittest source at http://pythonhosted.org/gchecky/unittest-pysrc.html:

735  class TestProgram:
752 -    def __init__(self, module='__main__', defaultTest=None,
753                   argv=None, testRunner=None, testLoader=defaultTestLoader):
754          if type(module) == type(''):
755              self.module = __import__(module)
756              for part in module.split('.')[1:]:
757                  self.module = getattr(self.module, part)
758          else:
759              self.module = module
760          if argv is None:
761              argv = sys.argv
762          self.verbosity = 1
763          self.defaultTest = defaultTest
764          self.testRunner = testRunner
765          self.testLoader = testLoader
766          self.progName = os.path.basename(argv[0])
767          self.parseArgs(argv)
768          self.runTests()
769
770 -    def usageExit(self, msg=None):
771          if msg: print msg
772          print self.USAGE % self.__dict__
773          sys.exit(2)
774
775 -    def parseArgs(self, argv):
776          import getopt
777          try:
778              options, args = getopt.getopt(argv[1:], 'hHvq',
779                                            ['help','verbose','quiet'])
780              for opt, value in options:
781                  if opt in ('-h','-H','--help'):
782                      self.usageExit()
783                  if opt in ('-q','--quiet'):
784                      self.verbosity = 0
785                  if opt in ('-v','--verbose'):
786                      self.verbosity = 2
787              if len(args) == 0 and self.defaultTest is None:
788                  self.test = self.testLoader.loadTestsFromModule(self.module)
789                  return
790              if len(args) > 0:
791                  self.testNames = args
792              else:
793                  self.testNames = (self.defaultTest,)
794              self.createTests()
795          except getopt.error, msg:
796              self.usageExit(msg)
797
798 -    def createTests(self):
799          self.test = self.testLoader.loadTestsFromNames(self.testNames,
800                                                         self.module)
801
802 -    def runTests(self):
803          if self.testRunner is None:
804              self.testRunner = TextTestRunner(verbosity=self.verbosity)
805          result = self.testRunner.run(self.test)
806          sys.exit(not result.wasSuccessful())
807
808  main = TestProgram

因此，当您执行 unittest.main() 时，会创建 TestProgram 的对象，该对象在第 768 行调用 self.runTests(). 构造函数还将您当前的文件作为包含测试的默认模块 (module='__main__').

So when you execute unittest.main(), an object of TestProgram gets created which calls self.runTests() at line 768. The constructor also takes your current file as the default module containing the tests ( module='__main__').

当runTests()被调用时，它依次调用self.testrunner.run().当您提到运行"时TextTestRunner 类的方法，你会发现它实际上运行并报告了你所有的测试结果.

When runTests() is called, it in turn calls self.testrunner.run(). When you refer to the "run" method of TextTestRunner class, you will find that it actually runs and reports all your test results.

测试发现由 TestProgram.parseArgs 在第 775 行调用 unittest.main() 完成.self.createTests 在第 798 行实际上负责发现所有测试用例并创建测试套件.这就是所有的魔法.

Test discovery is done by TestProgram.parseArgs at line 775 when you call unittest.main(). self.createTests at line 798 is actually responsible for discovering all your test cases and creating a test suite. This is all the magic.

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