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How to modularize your py.test fixtures

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.

@ghost

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commented Sep 21, 2017

thanks

@AndrewBMartin

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commented Oct 17, 2017

I'm having trouble making this work when running multiple tests at the same time. Would appreciate any insight you might have. Please see the SO question.

Thank you

@boxysean

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commented Oct 26, 2017

thank you

@ikonst

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commented Mar 6, 2018

You can simply create "local pytest plugins" which can be nothing more than Python files with fixtures, e.g.

  • tests/unit/conftest.py:

    pytest_plugins = [
       "tests.unit.fixtures.some_stuff",
    ]
  • tests/unit/fixtures/some_stuff.py:

    import pytest
    
    @pytest.fixture
    def foo():
        return 'foobar'
@ryanjdillon

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commented Oct 11, 2018

Awesome ikonst!

As a note that the respective directories referred to in tests.unit.fixtures.some_stuff" need to have __init__.py files for the plugins to be loaded by pytest.

https://docs.pytest.org/en/documentation-restructure/how-to/writing_plugins.html#requiring-loading-plugins-in-a-test-module-or-conftest-file

@kown7

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commented Apr 29, 2019

Fixtures with a

@pytest.fixture(scope="session", autouse=True)

scope need to be in the conftest.py file directly.

@jpadhye

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commented May 8, 2019

With python3 you run it as python -m pytest

Otherwise you see following error:


$ python -m py.test
/usr/local/Cellar/python/3.7.3/Frameworks/Python.framework/Versions/3.7/lib/python3.7/runpy.py:125: RuntimeWarning: 'py.test' found in sys.modules after import of package 'py', but prior to execution of 'py.test'; this may result in unpredictable behaviour
  warn(RuntimeWarning(msg))
/Users/jpadhye/.local/share/virtualenvs/sse-test-bench-4eGiHs-X/bin/python: loader for pytest cannot handle py.test
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