Test First

Tests prove behavior. You cannot claim a scenario, class, or method is implemented until tests pass.

• New code structure: follow .windsurf/rules/do-skeletons-first.md (docstrings, types, stubs).
• Write tests before implementation. Do not write tests whose only purpose is to hit NotImplementedError—write assertions that should pass once real behavior exists.
• Cover success (returns) and failure (raises, errors, edge cases) for each unit of behavior.
• If implementation contradicts docstring, ask the user which wins.
• Use docs/features/ to align scenarios with tests.
• Order: method-level → API → integration. For integration, follow .windsurf/rules/do-not-mock-in-integration-tests.md.
• Red–green: make the test fail, then implement until green.
• Use pytest; avoid mocks unless unavoidable.

Layout (never put tests in repo root):