mocker.patch.object appears to be broken

[binarymason]

Python version: 3.7.3

Packages on my machine:

• pytest: 5.2.1
• pytest-mock: 1.11.1

Testing a patched object method is called will fail using pytest_mock:

import pytest
from pytest_mock import mocker

def test_process_is_saved_to_db(mocker):
    with mocker.patch.object(Process, 'save', return_value="it works") as mock_save:
        thing = Process()
        thing.save()

    mock_save.assert_called_once()

AssertionError: Expected 'mock' to have been called once. Called 0 times.

---

But will pass with the exact same signature using unittest.mock:

import pytest
from unittest.mock import patch


def test_process_is_saved_to_db():
    with patch.object(Process, 'save', return_value="it works") as mock_save:
        thing = Process()
        thing.save()

    mock_save.assert_called_once()

All tests passed

[nicoddemus]

Hi @binarymason,

mocker.patch.object is not supposed to be used in a with context, please see Note about usage as a contextmangager.

[binarymason]

Ah, my bad. I need to RTFM.

Would it be helpful for future users if an exception were raised when mocker.patch.object is used in a with context?

Something along the lines of this?

class MockFixture(object):
    def __enter__(self):
        raise ValueError("with contexts are not supported, etc...")

[nicoddemus]

Hmmm that's a good idea. Would you like to open a PR in that effect?