Test-driven development discipline — write a failing test, implement the minimum to pass, then refactor. Use when adding a feature or fixing a bug where correctness matters.
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What the file says
# Test-Driven Development (TDD)
Write the test first. It forces precise specifications and gives a free regression net.
## Red → Green → Refactor
1. **Red.** Write ONE small test for the behavior you want. Run it. It must FAIL (and fail for the right reason — an assertion, not a compile error in unrelated code).
2. **Green.** Write the minimum code to make that test pass. No more, no less. Run it.
3. **Refactor.** Clean up duplication while keeping tests green. Re-run after each change.
Repeat with the next smallest increment.
## Rules of thumb
- Test behavior, not implementation. Prefer public API; don't poke private internals.
- One assertion concept per test. If "and" appears in the test name, consider splitting.
- Name tests like `it("returns X when Y")` / `should do Z when …`.
- If a bug fix, write the test that reproduces the bug FIRST (see `systematic-debugging`).
- Don't write tests that depend on wall-clock, random, or network unless you stub them.
## Running tests
- Match the project's framework and command (`bun test`, `pytest`, `go test`, …).
- For Bun projects: `bun test` (per `AGENTS.md`, Bun is the only JS runner).
## When TDD is overkill
…
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Source
GitHub
metaspartan/cybara · 32 stars · license MIT · pushed 2026-10-20 · branch main
API
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