Using Mock

production.py

class Production:

    def call_one(self, arg1, arg2):
        return arg1 + arg2

    def call_two(self, arg1, arg2, arg3):
        return self.call_one(str(arg1), str(arg2) + str(arg3))

testing.py

from unittest import mock
import unittest

from production import Production


class TestModule(unittest.TestCase):

    @mock.patch("production.Production.call_one")
    def test_case(self, mock_call_one):
        expected = "something"
        mock_call_one.return_value = expected

        prod = Production()
        response = prod.call_two(1, 2, 3)
        self.assertEqual(response, expected)

Ran 1 test in 0.001s

OK
Launching unittests with arguments python -m unittest testing.TestModule in /Users/senthil/workspace/pymockexample