PYTEST.md

Pytest

• Testcontainers + PyTest
  • Pytest Fixtures Using TestContainers
    • tests/conftest.py
    • tests/test_example.py

Conditionally Raising Exceptions

Kept forgetting what to query when trying to find this so I am adding it to my playbook of snippets

https://docs.pytest.org/en/stable/example/parametrize.html#parametrizing-conditional-raising

from contextlib import nullcontext

import pytest

@pytest.mark.parametrize(
    "example_input,expectation",
    [
        (3, nullcontext(2)),
        (2, nullcontext(3)),
        (1, nullcontext(6)),
        (0, pytest.raises(ZeroDivisionError)),
    ],
)
def test_division(example_input, expectation):
    """Test how much I know division."""
    with expectation as e:
        assert (6 / example_input) == e

Testcontainers + PyTest

Pytest Fixtures Using TestContainers

Make a test fixture available for the duration of the entire pytest session when you have the following in your conftest.py.

Assuming you have a docker-compose.yml in containers/docker/docker-compose.yml.

tests/conftest.py

# Third Party
import pytest
from testcontainers.compose import DockerCompose

@pytest.fixture(name="dockercompose", scope="session")
def _docker_compose():
    with DockerCompose(context="containers/docker/", compose_file_name="docker-compose.yml", pull=True, build=True) as compose:
        compose.wait_for("http://localhost:8080/")
        yield compose

And here is an example test using it:

tests/test_example.py

# Third Party
import pytest
import aiohttp
import base64

HOST = "http://localhost:8080/"
BASIC_AUTH = base64.b64encode("testuser:insecurepassword".encode()).decode()

headers={"Authorization": f"Basic {BASIC_AUTH}"}


@pytest.mark.asyncio
@pytest.mark.docker
async def test_example(dockercompose) -> None:
    """Start docker compose fixture and run endpoint check."""
    print(headers)
    async with aiohttp.ClientSession() as session:
        async with session.get(HOST, headers=headers) as response:
            data = await response.json()
    
    assert len(data) > 0

Since this test is marked as docker with a custom marker you can use the marks selector from pytest. Eg

python3 -m pytest -m docker