Python Pytest

Guidelines for writing and reviewing pytest suites. 15 rules across 5 categories, prioritized by impact.

A rule match is a signal, not a verdict. Most rules are design preferences for new tests — check the rule's impact level before flagging in review or churning a stable suite.

Quick-reference lines are triggers, not licenses: before applying a rule as a review finding or a transformation, open the rule file and check its counter-signal — the marker-opened paragraph (**When ...** / **Scope:** / **Exception ...**) saying when NOT to apply it.

When to Apply

• Writing new tests or fixtures
• Reviewing test files for value, isolation, or determinism
• Debugging flaky, order-dependent, or falsely-green tests
• Configuring pytest and its plugin surface

The unit of judgment is the contract a test defends — every rule here traces back to whether a failure would mean something.

Impact Levels