Deriving a class from TestCase throws two errors

Question

I have some basic setup/teardown code that I want to reuse in a whole bunch of unit tests. So I got the bright idea of creating some derived classes to avoid repeating code

Answer 1

In BaseController's __init__ you need to call unittest.TestCase's __init__ just like you did in TestMyController.

The call to construct a TestCase from the framework may be passing an argument. The best way to handle this for deriving classes is:

class my_subclass(parentclass):
    def __init__(self, *args, **kw):
        parentclass.__init__(self, *args, **kw)
        ...

Answer 2

It's because you're overriding __init__() incorrectly. Almost certainly, you don't want to override __init__() at all; you should do everything in setUp(). I've been using unittest for >10 years and I don't think I've ever overridden __init__().

However, if you really do need to override __init__(), remember that you don't control where your constructor is called -- the framework calls it for you. So you have to provide a signature that it can call. From the source code (unittest/case.py), that signature is:

def __init__(self, methodName='runTest'):

The safe way to do this is to accept any arguments and just pass 'em up to the base class. Here is a working implementation:

class BaseTest(unittest.TestCase):
    def __init__(self, *args, **kwargs):
        unittest.TestCase.__init__(self, *args, **kwargs)

    def setUp(self):
        print "Base.setUp()"

    def tearDown(self):
        print "Base.tearDown()"


class TestSomething(BaseTest):
    def __init__(self, *args, **kwargs):
        BaseTest.__init__(self, *args, **kwargs)
        self.controller = object()

    def test_silly(self):
        self.assertTrue(1+1 == 2)