[pytest-dev] Testing fixture teardown / finalisation
James Cooke
me at jamescooke.info
Wed Jan 6 12:36:28 EST 2021
Hi all,
It's been a while since I've had to write a complicated and robust pytest fixture and I'm struggling with testing the teardown / finalisation code.
Instead of boring you with the [my-work-project] requirements of cleaning up GCS after tests, I'll refer to the fixture in the docs https://docs.pytest.org/en/stable/fixture.html#fixture-finalization-executing-teardown-code :
@pytest.fixture(scope="module")
def smtp_connection():
smtp_connection = smtplib.SMTP("smtp.gmail.com", 587, timeout=5)
yield smtp_connection # provide the fixture value
print("teardown smtp")
smtp_connection.close()
My (very old) usual strategy for testing teardown of a fixture that uses `yield` would be:
* Start test
- Instantiate the fixture.
- Manipulate the instance with `next()` to trigger the teardown.
- Ensure that teardown was successful - in this case assert that the SMTP connection returned when the fixture was instantiated was closed successfully.
Given that since v4.1 (https://github.com/pytest-dev/pytest/issues/4545), the arrangement step of "Instantiate the fixture" does not work, could someone point me at the recommended method of testing fixture teardown?
I would like to ensure that teardown is resilient and can resolve multiple conditions that can happen in [my-work-project]'s test suite. I can see that there are multiple tests on fixtures in https://github.com/pytest-dev/pytest/blob/48c9a96a03261e7cfa5aad0367a9186d9032904a/testing/python/fixtures.py , are there any preferred / recommended / efficient methods in this file? Alternatively, is there a way to by-pass the fixture wrapping that happens that prevents it being callable? Should I be using `smtp_connection.__pytest_wrapped__.obj()` to instantiate? (this seems bad)
Any pointers / suggestions would be great.
Thanks,
James
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