pytest using fixtures as arguments in parametrize

Question

I would like to use fixtures as arguments of pytest.mark.parametrize or something that would have the same results.

For example:

import pytest
import my_package

@pytest.fixture
def dir1_fixture():
    return '/dir1'

@pytest.fixture
def dir2_fixture():
    return '/dir2'

@pytest.parametrize('dirname, expected', [(dir1_fixture, 'expected1'), (dir2_fixture, 'expected2')]
def test_directory_command(dirname, expected):
    result = my_package.directory_command(dirname)
    assert result == expected

The problem with fixture params is that every param of the fixture will get run every time it's used, but I don't want that. I want to be able to choose which fixtures will get used depending on the test.

Answer 1

If you're on pytest 3.0 or later, I think you should be able to solve this particular scenario by writing a fixture along the lines of:

@pytest.fixture(params=['dir1_fixture', 'dir2_fixture'])
def dirname(request):
    return request.getfixturevalue(request.param)

Docs here: http://doc.pytest.org/en/latest/builtin.html#_pytest.fixtures.FixtureRequest.getfixturevalue

However, you can't use this approach if the fixture you're attempting to dynamically load is parametrized.

Alternatively, you might be able to figure something out with the pytest_generate_tests hook. I haven't been able to bring myself to look into that much, though.

Answer 2

Will was on the right path , you should use request.getfixturevalue to retrieve the fixture.

But you can do it right in the test, which is simpler.

@pytest.mark.parametrize('dirname, expected', [
    ('dir1_fixture', 'expected1'),
    ('dir2_fixture', 'expected2')])
def test_directory_command(dirname, expected, request):
    result = my_package.directory_command(request.getfixturevalue(dirname))
    assert result == expected

Another way is to use lazy-fixture plugin:

@pytest.mark.parametrize('dirname, expected', [
    (pytest.lazy_fixture('dir1_fixture'), 'expected1'),
    (pytest.lazy_fixture('dir2_fixture'), 'expected2')])
def test_directory_command(dirname, expected):
    result = my_package.directory_command(dirname)
    assert result == expected

Answer 3

As for now, my only solution is to create a fixture that returns a dictionary of fixtures.

import pytest
import my_package

@pytest.fixture
def dir1_fixture():
    return '/dir1'

@pytest.fixture
def dir2_fixture():
    return '/dir2'

@pytest.fixture
def dir_fixtures(
    dir1_fixture,
    dir2_fixture
    ):
    return {
        'dir1_fixture': dir1_fixture,
        'dir2_fixture': dir2_fixture
    }

@pytest.mark.parametrize('fixture_name, expected', [('dir1_fixture', 'expected1'), ('dir2_fixture', 'expected2')]
def test_directory_command(dir_fixtures, fixture_name, expected):
    dirname = dir_fixtures[fixture_name]
    result = my_package.directory_command(dirname)
    assert result == expected

Not the best since it does not use a solution built into pytest, but it works for me.

Answer 4

This isn't currently supported by pytest. There is an open feature request for it though: https://github.com/pytest-dev/pytest/issues/349 .