How to modularize your py.test fixtures

pytest-fixture-modularization.md

Using py.test is great and the support for test fixtures is pretty awesome. However, in order to share your fixtures across your entire module, py.test suggests you define all your fixtures within one single conftest.py file. This is impractical if you have a large quantity of fixtures -- for better organization and readibility, you would much rather define your fixtures across multiple, well-named files. But how do you do that? ...No one on the internet seemed to know.

Turns out, however, you can define fixtures in individual files like this:

tests/fixtures/add.py

import pytest

@pytest.fixture
def add(x, y):
    x + y

Then you can import these fixtures in your conftest.py:

tests/conftest.py

import pytest
from fixtures.add import add

...and then you're good to test!

tests/adding_test.py

import pytest

@pytest.mark.usefixtures("add")
def test_adding(add):
    assert add(2, 3) == 5

Because of the modularity, tests will have to be run with python -m py.test instead of py.test directly.

Great gist on modularization of conftest, it works great, thanks!

And thanks to @ryanjdillon for the tip about init.py, it solved a mypy problem for me.

Another option would be to have multiple nested directories/packages containing your tests, and each directory can have its own conftest.py with its own fixtures, adding on to the ones provided by the conftest.py files in parent directories as written in the official doc here