TDD playbook

HARD-GATE

• No implementation until a test exists, was run, and failed because behaviour is missing (not because of compile noise you have not fixed in the test).
• Implementation waits for explicit user approval.
• Quality gate before you call it done — same commands as docs/skill-authoring.md: cargo fmt --check, cargo clippy --all-targets -- -D warnings, cargo test.

When to use

New or changed behaviour in a Rust crate. Prefer unit tests next to the module; tests/ only for public-API contracts.

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