Test-Driven Development

Process skill — red → green microcycle. Tests at public interfaces only. Shared vocabulary → process-skill-composition.md.

References: anti-patterns.md · output.md · codebase-design.md · engineering-principles.md (test behavior, not implementation; sequence verifiable units).

Read research-basis.md only when you calibrate seam claims.

Entry gate

Seam — the public interface under test. One the user names is agreed. Otherwise propose one (Seam: header) and get agreement.
Slice in scope — path glob or module id shared with other active atoms when layered.
Decide, don't stall. Pick a reasonable, reversible answer and name it in your reply; ask first only for irreversible or product decisions. Never end a requested change with no change made.
If no seam is named or agreed, stop and ask. Do not write production code or tests at private helpers only.