Cointainers as Pytest fixtures made easy
This package was inspired by others, but after trying to make heads and tails of them when faced with bugs, I ended-up finding simpler to start over.
Using dockerfixtures with pytest
To spawn a container in your tests, proceed as follow:
import docker from dockerfixtures import image, container import pytest @pytest.fixture(scope='session') def docker_client(): return docker.from_env() @pytest.fixture(scope='session') def pg_image() -> image.Image: return image.Image('postgres', tags='12') @pytest.fixture(scope='function') def pg_container(docker_client: docker.client.DockerClient, pg_image: image.Image) -> container.Container: yield from container.fixture(docker_client, some_image) # If you don't need to reuse the image @pytest.fixture(scope='session') def pg_container(docker_client) -> container.Container: some_image = image.Image('postgres', tags='12') yield from container.fixture(docker_client, some_image)
Why not a pytest plugin ?
Other implementation of this have been provinding a pytest plugin, so you might wonder why this one doesn’t ?
First reason is I have not looked into it that much, yet.
But anyhow, you would still need to import the dockerfixtures.image module. So I am not very sure what the benefits would be ?
Also I found those plugins to provide somewhat bizarre API, for example to define the fixtures’ scope. I haven’t looked into why they do that, yet. Here there are no surprises, a container fixture looks like any other fixture.
Pytest plugins are global: they have to be imported in your top-level conftest.py (see note). I think it is good practice to keep your tests properly partitioned based on their external dependencies. It can help split workload if the need arises. In a collaborative environment, having to import dockerfixtures, may help prevent breaking that partitioning during reviews.
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