rust-tddlisted

# Rust TDD ## Purpose This skill is **rigid**. Follow every step exactly. Do not skip RED. Do not write implementation before a failing test exists. The value of TDD is not the test file. The value is that the test failed first, for the reason you predicted. A test written after the implementation only proves that the code does what the code does. ## The cycle Repeat this cycle for every behavior change: 1. **RED** — Write exactly one failing test. Run it. Confirm that it fails, and that it fails for the expected reason. A compile error is not a valid RED. Make the test compile, then let the assertion fail. 2. **GREEN** — Write the minimum implementation that makes the test pass. Run the test again. Do not add code that no test requires. 3. **REFACTOR** — Clean up the test and the implementation. Run the crate tests to confirm that nothing broke. 4. **LINT** — Run the format and lint gate before you call the cycle complete. ```bash cargo fmt --all -- --check cargo clippy --workspace --all-targets --all-features --locked -- -D warnings ``` `--all-targets` includes tests, benches, and examples. The lint gate applies to test code too. See the `rust-lints` skill for the lint set and for allow-with-reason policy. Never batch multiple behaviors into one cycle. One test, one behavior, one cycle. ### RED is a prediction, not a formality Before you run the failing test, write down the expected failure in one sentence: which assertion fails, and with which value.