gistfile1.py

class MyTestCase(unittest.TestCase):

  def setUp(self):
    self.foo_patcher = patch('__main__.Class', spec=True)
    self.foo_patcher.start()

  def tearDown(self):
    self.foo_patcher.stop()
    
class TestThingie(MyTestCase):

  def test_thingie(self):
    thingie()
    self.assertEqual(1, self.foo_patcher.call_count)

class TestAnotherThing(MyTestCase):
  
  def setUp(self):
    super(TestAnotherThing, self).setUp()  # <-- this is important
    ...
    
  ...