mymodule.py

def repeater(str):
    return str + str

def hello():
    return repeater("Hello")

mymodule_test.py

import mox
import mymodule

class TestHello(mox.MoxTestBase):

    def test_failing_hello(self):
        self.mox.StubOutWithMock(mymodule, 'repeater')

        mymodule.repeater("World").AndReturn("HelloWorld")

        self.mox.ReplayAll()

        mymodule.hello()

    def test_successful_hello(self):
        self.mox.StubOutWithMock(mymodule, 'repeater')

        mymodule.repeater("Hello").AndReturn("HelloWorld")

        self.mox.ReplayAll()

        self.assertEqual("HelloWorld", mymodule.hello())

setup.py

from setuptools import setup, find_packages

version = '0.1.0-SNAPSHOT'

setup(name='mox_test',
      version=version,
      description="Testing Mox",
      packages=find_packages(exclude=['ez_setup', 'examples', 'tests']),
      zip_safe=False,
      test_suite='nose.collector',
      tests_require=['nose', 'mox'],
      )