Allow use of custom mock implementations

With the growing use of asyncio, we need ways to mock Coroutines.

Currently, mock and unittest.mock do not support creating specs for coroutines (AsyncMock is being added in python 3.8).

As a work around, we’re using asynctest.mock, which has the same interface as unittest.mock, however this requires us to completely re-implement the __init__ method of MockFixture, and removes the “hide traceback” functionality (though we don’t care too much about this). This allows us to have both mocker and async_mocker fixtures.

TLDR To ease this usecase (and potentially others), Can support for defining a mock modules path from the config be added please?

[antdking]

agree with your points on this. I think it’s probably best to wait until 3.8 for this library.

In terms of creating a new plugin, it might be better to try and get the fixtures into the asynctest library instead. Will close this issue for now.

The hack we have in place works well enough for us until that time, and for our specific usecase, it will be an easy migration.

If anyone else stumbles on this issue, here is the hack:

import pytest

import pytest_mock
import asynctest.mock


@pytest.fixture
def async_mocker(pytestconfig):
    # This is a straight copy + paste from pytest_mock, but with our patched MockFixture
    result = AsyncMockFixture(pytestconfig)
    yield result
    result.stopall()


class AsyncMockFixture(pytest_mock.MockFixture):
    def __init__(self, config):
        # This is a straight copy + paste from pytest_mock
        # TODO: contribute a way to use arbitary mock libraries upstream

        self._patches = []  # list of mock._patch objects
        self._mocks = []  # list of MagicMock objects

        # CHANGED: hard coding the asynctest.mock
        self.mock_module = mock_module = asynctest.mock

        self.patch = self._Patcher(self._patches, self._mocks, mock_module)
        # aliases for convenience
        self.Mock = mock_module.Mock
        self.MagicMock = mock_module.MagicMock
        self.NonCallableMock = mock_module.NonCallableMock
        self.PropertyMock = mock_module.PropertyMock
        self.call = mock_module.call
        self.ANY = mock_module.ANY
        self.DEFAULT = mock_module.DEFAULT
        self.create_autospec = mock_module.create_autospec
        self.sentinel = mock_module.sentinel
        self.mock_open = mock_module.mock_open

        # CoroutineMock is from asynctest
        # AsyncMock is being added in python 3.8
        # Please use AsyncMock.
        self.CoroutineMock = self.AsyncMock = mock_module.CoroutineMock

[tirkarthi]

FWIW, AsyncMock is now available as part of mocker from https://github.com/pytest-dev/pytest-mock/commit/449d3d038e076fcdbb860815d306d4a59db44141 with rich assert diff for assert helpers associated with AsyncMock