rune-test

Write one failing test that defines the expected behavior, run it to confirm it fails (RED), then implement the minimal code to make it pass (GREEN), and commit both as a test/feat pair. Repeat one test at a time rather than batching tests upfront.

It scans for config files: jest.config or a jest key in package.json for Jest, vitest.config for Vitest, pytest.ini or pyproject.toml for pytest, Cargo.toml for Rust, *_test.go files for Go, and cypress.config or playwright.config for E2E tools.

Vertical slicing means completing one full RED-GREEN-commit cycle before writing the next test. Writing multiple tests upfront produces tests of imagination that verify imagined shapes rather than real behavior learned from prior cycles.

Yes, but pytest-asyncio must be installed and asyncio_mode configured in pyproject.toml. With asyncio_mode set to auto, plain async def test functions work; otherwise each async test needs the @pytest.mark.asyncio decorator to avoid silently passing.

Mock only at system boundaries you do not own, such as third-party paid APIs or external services. Never mock your own classes, always mock the complete data shape, and keep mock setup shorter than the test logic itself.

A test passing without implementation means it is not testing real behavior, only mocks or trivial conditions. Such tests must be rewritten stricter so they genuinely fail until the implementation exists.