Is it possible to write a function-level pytest fixture that applies a mock decorator to the function?

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In our repo, we have some calls to s3. We never want these to execute during testing, so we mock them out in each individual test, which gets annoying. It's a lot of repeated code, and can be dangerous if a developer forgets to write the mock before running the test.

I would like to write a pytest fixture that automatically applies the mock to every testing function. That is, I want to change my code from looking like this:

test_file.py:

@mock.patch.object(S3Hook, 'write_to_s3')
def test1(_):
    # test some stuff without writing to s3

@mock.patch.object(S3Hook, 'write_to_s3')
def test2(_):
    # test some more stuff without writing to s3

to this:

conftest.py:

@pytest.fixture(scope='function', autouse=True)
def mock_out_s3(request):
    # somehow apply the mock.patch.object decorator to request.function here


test_file.py:

def test1():
    # test some stuff; the mock is automatically applied, so we won't write to s3

def test2():
    # ditto

Is this possible?

pytest fixtures decorator mocking python
2 Answers

Posting the details of how I got this to work (based on ParthS007's answer) to help out anyone else who is trying to do the same thing in the future:

@pytest.fixture(scope='function', autouse=True)
def mock_out_s3(request):
    patcher = mock.patch.object(S3Hook, 'write_to_s3')
    patcher.start()
    request.addfinalizer(patcher.stop)
user_116939020

While writing these Unittests. You can do this:


Class TestClass(TestCase):

    @classmethod
    def setUpTestData(cls):
        pass

    def tearDown(self):
        self.patcher.stop()

    def setup(self):
       self.patcher = mock.patch(S3Hook, 'write_to_s3')
       mock_apply = self.patcher.start()

    def test1(self):
    # test some stuff; the mock is automatically applied, so we won't write to s3

    def test2(self):
    # ditto

You can find more detail about the patcher here: https://docs.python.org/3/library/unittest.mock.html#the-patchers

user_79940740
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