Guidelines for fixtures usage in OCS-CI

Basic information

What is a pytest Fixture? You can find definition and examples documentation in pytest web. Please read this documentation first.

We should keep our fixtures organized and have all the dependencies well defined in fixtures.

All the fixtures should be documented - documenting the return value is mandatory.

Fixture is composed of its setup part, the code which is done for prepare resource and teardown part which is after yield of added via request.addfinalizer method. It’s strictly forced to use addfinalizer method cause it can happen that what is after yield won’t be proceed when exception will be thrown in the middle of the setup.

The finalizer should be added as soon as possible to make sure the finalizer will be called at the end. (Otherwise we will hit the same issue as we have with yield)

Use cases

TODO: Mention function factories and use cases and when to use which approach. Something like:

Setup resource, test (using resources), teardown - regular usage of fixture
Test creating resources as part of test, teardown of resources - fixture factory solve the issue here, see the documentation
Setup resources, test (using resources , deleting resources), teardown shouldn’t fail on those deleted resources

Avoid

Here is the list of things we should avoid in our fixtures:

Using references to request.node.cls for setting, altering or reading class attributes.
Using globals for sharing data.
Using yield.
Using @pytest.mark.usefixtures.
Using more than one assert in the teardown when another teardown action is between them. (This will lead to a situation where the rest of resources aren’t cleaned.

Examples of fixtures and tests

Here are few simple examples of how to use fixtures.

conftest.py - Example of fixture definitions in conftest.py file for fixtures meant to be shared between tests.
test_fixtures.py - Examples of tests.