Add a function to detect if pytest is running

What’s the problem this feature will solve?

Django settings modules often load environment variables from a .env file:

from pathlib import Path

import dotenv

BASE_DIR = Path(__file__).resolve().parent.parent

dotenv.load_dotenv(dotenv_path=BASE_DIR / ".env")

Loading from .env is not desirable during test runs. Environment variables added for local debugging may affect the test run in unexpected ways, such as making remote API calls.

The settings module should therefore only load the .env file if pytest isn’t running:

from pathlib import Path

import dotenv

BASE_DIR = Path(__file__).resolve().parent.parent

if ... # pytest is not running
    dotenv.load_dotenv(dotenv_path=BASE_DIR / ".env")

Changing behaviour during tests is usually undesirable, but here it’s done to isolate the test run, which is a good thing.

pytest documents a pattern to change behaviour using fixtures here: https://docs.pytest.org/en/latest/example/simple.html#detect-if-running-from-within-a-pytest-run . Unfortunately this techinque is incompatible with this particular problem. pytest-django’s fixtures load the settings module early, before fixtures from conftest.py fixtures run, so the pattern cannot be applied. And environment variable changes cannot be undone after the fact.

To solve this I made pytest-is-running, which can be used like so:

from pathlib import Path

import dotenv
import pytest_is_running

BASE_DIR = Path(__file__).resolve().parent.parent

if not pytest_is_running.is_running():
    dotenv.load_dotenv(dotenv_path=BASE_DIR / ".env")

pytest-is-running works because plugin fixtures can load early, and it uses hooks with tryfirst=True.

Describe the solution you’d like

Rather than have a documented workaround and plugin, I’d like to see a function in core pytest that provides the ability to check if pytest is running. It could simplify things for those using the both the documented pattern and the plugin.

It would also be good if the solution could somehow avoid the cost of doing import pytest, so that non-test pathways do not import the heap of stuff in pytest only to ignore it because pytest isn’t running. The plugin is deliberately structured to avoid this.

Alternative Solutions

I wrote the plugin.

Additional context

none

[The-Compiler]

We currently just document how to do this, probably in a way similarly to what your plugin does.

Note you could also just check if "pytest" in sys.modules: as long as your code under test does not import pytest.

We do have a PYTEST_CURRENT_TEST environment variable already. Personally I’d be fine with having a PYTEST_VERSION or whatever which gets set very early, I suppose PYTEST_CURRENT_TEST will be set too late for it to be useful at import time.

[The-Compiler]

Also see https://github.com/pytest-dev/pytest-django/issues/333 which has some additional considerations and use-cases around this.