gistfile1.txt

class Foo(object):
    def __init__(*args, **kwargs):
        self.a = kwargs.get('a')
        self.b = kwargs.get('b')
        self.c = kwargs.get('c')

    @property
    def prop_1(self):
        return self.a + self.b

    @property
    def prop_2(self):
        return self.prop_1 + self.c

foo = Foo(*args, **kwargs)  # big class

mock_foo = Mock(a="some", b="value", c="OMG")
mock_foo.prop_1 = "some value"
mock_foo.prop_2 = "some value OMG"

assertEqual(foo.prop_1, mock_foo.prop_1)
assertEqual(foo.prop_2, mock_foo.prop_2)