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I have a unit test I'm running with a particular fixture. The fixture is pretty simple and looks like so:

@pytest.fixture
def patch_s3():
    # Create empty bucket
    bucket = s3_resource().create_bucket(Bucket=BUCKET)
    bucket.objects.all().delete()

    yield

    bucket.objects.all().delete()

and the test isn't all that complicated either. Here is the signature for the test:

def test_task_asg(patch_s3, tmp_path, monkeypatch)

However, when I run pytest, I get the following error:

tests/test_task_asg.py:313: in <module>
    @pytest.fixture
home/ubuntu/miniconda/envs/pipeline/lib/python3.7/site-packages/_pytest/fixtures.py:1150: in fixture
    fixture_function
home/ubuntu/miniconda/envs/pipeline/lib/python3.7/site-packages/_pytest/fixtures.py:1011: in __call__
    "fixture is being applied more than once to the same function"
E   ValueError: fixture is being applied more than once to the same function

This is weird to me, as it seems to imply I'm somehow including patch_s3 more than once in test_task_asg. What could be causing this?

code11
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1 Answers1

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If you scroll up from your definition of patch_s3, you'll probably find another duplicate line like @pytest.fixture, causing the issue. That line can only be used once per fixture method definition.

The easiest way to reproduce this issue is with:

import pytest

@pytest.fixture(scope="session")
@pytest.fixture
def my_fixture():
    yield

def test_abc(my_fixture):
    pass

Running that with pytest yields ValueError: fixture is being applied more than once to the same function. But if you remove one of the two @pytest.fixture lines, then the issue goes away.

Here are some examples where other people had the same issue and fixed it:

Michael Mintz
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    Ah, you're totally right. I was looking for something in the signature itself, or something in the way I was running the tests. Good call. Based on my knowledge of SO's rules I think it makes sense to keep the question, as others may run into the same thing, and I didn't see a good SO dupe. – code11 Jul 05 '23 at 17:09