How to reset a mocked object during test in Python 3 ?

ResetMock.py

#!/usr/bin/env python3


import unittest
from subprocess import check_output
from unittest.mock import patch


class YourClass(object):
    def __init__(self):
        self.values = []

        self.values.append(
            check_output(['echo', 'foo'], universal_newlines=True).rstrip()
        )
        self.values.append(
            check_output(['echo', 'bar'], universal_newlines=True).rstrip()
        )
        self.values.append(
            check_output(['echo', 'dead'], universal_newlines=True).rstrip()
        )
        self.values.append(
            check_output(['echo', 'beef'], universal_newlines=True).rstrip()
        )


class FakeCheckOutputMock(object):
    @patch(  # Here we mock the original `check_output` object
        'subprocess.check_output',
        return_value='Mocked !'
    )
    def __init__(self, check_output_mock):
        # In this list, you specify what object will act in your mock
        # We use a list for its ordering aspect.
        self.answers = [
            check_output,  # 1st `check_output` call will behave "regularly"
            check_output_mock,  # 2nd call will be mocked
            check_output,       # ... and so one
            check_output_mock,
        ]

    def method(self, *args, **kwargs):
        # Here we :
        #     * Pop the first element of the list above
        #     * Use it as a function...
        #     * Called with the parameters passed to the mock
        #         (like `universal_newlines` for instance)
        return self.answers.pop(0)(*args, **kwargs)


class MyTest(unittest.TestCase):
    @patch(
        # Let's patch the `check_output` object of this module
        '__main__.check_output',
        # The class is instantiated only one time
        #   and the `side_effect` will be one of its methods.
        side_effect=FakeCheckOutputMock().method
    )
    def test_my(self, check_output_mock):
        self.assertListEqual(YourClass().values, [
            'foo',
            'Mocked !',
            'dead',
            'Mocked !'
        ])


if __name__ == '__main__':
    unittest.main()