python-testing

Define a function decorated with @pytest.fixture that performs setup, uses yield to hand the resource to the test, then runs teardown code after the yield. Fixture scopes like function, module, or session control how often setup runs.

Use unittest.mock.patch as a decorator targeting the import path of the external call, then set return_value or side_effect on the mock. Assert call counts with assert_called_once or assert_awaited_once for async functions.

Yes, pytest-asyncio enables async tests via the @pytest.mark.asyncio decorator. Async fixtures can also be defined with async def and yield, and async mocks are verified with assert_awaited_once.

Tag tests with custom markers like @pytest.mark.slow or @pytest.mark.integration, register them in pytest.ini, then filter with pytest -m "not slow" or combine expressions like "unit and not slow".

Target 80%+ overall coverage with 100% on critical paths. Measure it using pytest --cov=mypackage --cov-report=term-missing to see uncovered lines, and generate HTML reports for detailed inspection.