pytest_unit_test_rules

Pytest Unit Test Rules (Concise)

Framework

• Use pytest exclusively; prefer fixtures; use pytest assert statements.

Naming

• Files test_*; classes Test*; functions test_*.

Imports

• Order: standard library, third‑party, project.
• Import only the unit under test; mock collaborators using pytest-mock.

Import and Mock Rules

• Do not directly import external interfaces/clients/services into tests to exercise collaborators.
• Patch where the dependency is imported (lookup site) using a fully‑qualified path.
• Use side_effect to cover error paths when appropriate.

from pytest_mock import MockFixture
from backend.apps.some_app import create_resource

def test_create_resource_success(mocker: MockFixture):
    mocker.patch(
        "backend.services.model_provider_service.ModelProviderService.create",
        return_value={"id": "res-1"},
    )
    assert create_resource({...})["id"] == "res-1"

Structure and Size

• Keep files under 500 lines or split by feature; include __init__.py in split directories; use test_<module>_<feature>.py names.

Coverage and Async

• Cover success/error flows and boundaries; use @pytest.mark.parametrize for variants.
• Use @pytest.mark.asyncio for async tests.

Isolation

• Use autouse=True fixtures to reset state; fully mock external I/O and APIs.

Checklist

• pytest only (no unittest)
• naming conventions followed
• collaborators mocked with pytest-mock
• import/mocking rules followed
• async tests decorated when needed
• clear, specific assertions
• adequate coverage (normal and exception paths)