another_file.py

# --------------------------------------------------------------------------- #
class Foo(object):

    # ....................................................................... #
    def get_string(self):
        return "hello"

    # ....................................................................... #
    def reverse_string(self, str_=self.get_string()):
        return str_[::-1]

another_file2.py

# --------------------------------------------------------------------------- #
class Foo(object):

    # ....................................................................... #
    def get_string(self):
        return "hello"

    # ....................................................................... #
    def reverse_string(self, str_=None):
        if str_ is None:
            str_ = self.get_string()
        return str_[::-1]

another_file3.py

# --------------------------------------------------------------------------- #
class Foo(object):
 
    # ....................................................................... #
    def get_string(self):
        return "hello"
 
    # ....................................................................... #
    @staticmethod
    def reverse_string(self, str_):
        return str_[::-1]
 

test_self_injection.py

# -*- coding: utf-8 -*-

"""
Sample Test Cases More Injections
"""

from unittest import TestCase


# --------------------------------------------------------------------------- #
class Foo(object):

    # ....................................................................... #
    def get_string(self):
        return "hello"

    # ....................................................................... #
    def reverse_string(self):
        str_ = self.get_string()
        return str_[::-1]


# --------------------------------------------------------------------------- #
class TestFoo_get_string(TestCase):

    # ....................................................................... #
    def _callFUT(self, *args, **kwargs):
        return Foo.get_string.im_func(*args, **kwargs)

    # ....................................................................... #
    def test_get_string(self):

        dummy_self = object()

        desired_output = 'hello'

        self.assertEqual(self._callFUT(dummy_self), desired_output)


# --------------------------------------------------------------------------- #
class TestFoo_reverse_string(TestCase):

    # ....................................................................... #
    def _callFUT(self, *args, **kwargs):
        return Foo.reverse_string.im_func(*args, **kwargs)

    # ....................................................................... #
    def test_reverse_string(self):

        class DummySelf(object):

            def get_string(self):
                # this is "test_string" in reverse
                return 'gnirts_tset'

        dummy_self = DummySelf()

        desired_output = 'test_string'

        self.assertEqual(self._callFUT(dummy_self), desired_output)