如何模拟pytest.fixture装饰器？

Question

I wanted to write unit tests for pytest fixtures present in conftest.py
How do I mock decorator pytest.fixture?

Conftest.py

import pytest 

@pytest.fixture(scope="session", autouse="True")
def get_ip(dict_obj):
    """Assume some functionality"""
    return dict_obj.get('ip')


@pytest.fixture(scope="class")
def get_server(create_obj):
    """Assume some functionality"""
    pass

test_conftest.py

mock_fixture = patch('pytest.fixture', lambda x : x).start()
from tests.conftest import get_ip  


class TestConftestTests:

    def test_mgmt_ip(self):
        assert mgmt_ip({"ip": "10.192.174.15"}) == "10.192.174.15"

 E   TypeError: <lambda>() got an unexpected keyword argument 'scope' 

When I tried to mock pytest.fixture at the starting of the test module before importing functions to be tested, I am getting error - E TypeError: <lambda>() got an unexpected keyword argument 'scope'

If I remove the lambda function , I am getting E AssertionError: assert <MagicMock name='fixture()()()' id='4443565456'> == '10.192.174.15'

test_conftest.py

patch('pytest.fixture').start()
from tests.conftest import get_ip  


class TestConftestTests:

    def test_mgmt_ip(self):
        assert mgmt_ip({"ip": "10.192.174.15"}) == "10.192.174.15"

E       AssertionError: assert <MagicMock name='fixture()()()' id='4443565456'> == '10.192.174.15' 

Could someone help me to resolve the error ? Thanks!

Answer 1

@pytest.fixture(scope='session') is going to call your lambda x: x with the kwarg scope . A mock covering both the no-args and some-args versions of pytest.fixture might be:

pytest_fixture = lambda x=None, **kw: x if callable(x) else fixture

But it should be noted pytest.fixture doesn't do any registration by itself. It only marks the function as a fixture, by setting the _pytestfixturefunction attribute on it; afterward, pytest collects the fixture.

I'm not sure you're barking up the right tree for whatever you might be trying to accomplish. If you want to change what value a fixture has in certain contexts, classes and subclasses can be used to override parent fixtures. If you're trying to see whether a fixture is used, creating a new class and overriding the fixture with your assertion can be useful.