使用具有多个子类的baseclass时，ImportError无法导入名称

Question

I need to have a base class that runs setup/teardown, then subclasses that inherit, in order to allow for all tests to run regardless if certain ones fail. When attempting to have multiple subclasses that import a base class, I see an import error for the second subclass. I have the following files: runtestcases.py testcase1.py testcase2.py

Here is runtestcases.py:

import unittest
import testcase1, testcase2

class ArithTestSuper (unittest.TestCase):

def setUp (self):
    print("Setting up ArithTest cases")

def tearDown (self):
    print("Cleaning up ArithTest cases")


def my_suite():

suite = unittest.TestSuite()

suite.addTest (testcase1.ArithTest())
suite.addTest (testcase2.ArithTestFail())

return suite


if __name__ == '__main__':
    runner = unittest.TextTestRunner()
    test_suite = my_suite()
    runner.run (test_suite)   

Here is testcase1.py:

from runtestcases import ArithTestSuper

class ArithTest (ArithTestSuper):

def runTest (self):
    """ Test addition and succeed. """
    print("Running ArithTest")
    self.failUnless (1+1==2, 'one plus one fails!')
    self.failIf (1+1 != 2, 'one plus one fails again!')
    self.failUnlessEqual (1+1, 2, 'more trouble with one plus one!')

Here is testcase2.py:

from runtestcases import ArithTestSuper

class ArithTestFail (ArithTestSuper):

def runTest (self):
    """ Test addition and fail. """
    print("Running ArithTestFail")
    self.failUnless (1+1==2, 'one plus one fails!')
    self.failIf (1+1 != 2, 'one plus one fails again!')
    self.failUnlessEqual (1+1, 2, 'more trouble with one plus one!')
    self.failIfEqual (1+1, 2, 'expected failure here')
    self.failIfEqual (1+1, 2, 'second failure')  


Compilation fails on testcase2.py with:
ImportError: cannot import name ArithTestSuper

If I run just testcase1 it works - likewise, running just testcase2 works. If I try both this error occurs. Thoughts?

Answer 1

This is a problem with circular imports. Move your base class out of the module you run.

Answer 2

To answer your second question ( https://stackoverflow.com/a/12885312/1745627 ): avoid overriding the runTest method; it is to be called by the unittest framework, and essentially does the job of runing your testcase. Implement your own test methods using a naming convention like test_xxx (unittest looks for methods starting with test to execute).