Fixture mechanics - Playwright and pytest

Deep mechanics for Step 3 of test-framework-blueprint. The blueprint decisions (which scope, what each fixture provides, whether tests mutate it) live in SKILL.md; this file carries the framework-specific wiring.

Playwright mechanics to standardize in the conventions doc

All per the test-fixtures docs:

• Custom fixtures via test.extend(); teardown code follows await use(...) in the same function, so setup and teardown live together.
• Cross-cutting fixtures that every test needs (e.g. a network-stub guard) are declared { auto: true }: they are "set up for each test/worker, even when the test does not list them directly."
• Fixture modules from separate concerns combine via mergeTests(); this is what makes the fixtures/index.ts single-import convention work.
• Tunable values (base URL, default user role) become option fixtures ({ option: true }) configured through test.use() per project.

The pytest equivalent

If Step 2 chose Python, the same architecture maps onto pytest fixtures. Per the pytest fixtures how-to, tests request fixtures by declaring them as arguments; available scopes are function (the default), class, module, package, and session, where scope controls destruction (a function-scoped fixture "is destroyed at the end of the test"; a session-scoped one at the end of the test session). The fixtures/index.ts merged-export convention becomes conftest.py (fixtures there are accessible to "tests from multiple test modules in the directory"), teardown code goes after yield, and { auto: true } becomes @pytest.fixture(autouse=True). Playwright's worker scope has no direct pytest twin; session scope plus per-worker IDs (e.g. pytest-xdist worker id) fills the same database-per-worker role.