aoa-tdd-slice

Intent

Use test-first discipline to implement a small feature slice with a clear behavioral target and explicit verification.

Trigger boundary

Use this skill when:

• a behavior change can be expressed as tests before implementation
• the task fits a bounded slice rather than a broad rewrite
• confidence and regression resistance matter

Do not use this skill when:

• the task is purely exploratory and behavior is still undefined
• the task is mostly one-off glue with no reusable logic
• the main problem is a stable interface or boundary contract rather than a feature slice; use aoa-contract-test
• the main problem is invariant coverage rather than slice implementation; use aoa-property-invariants
• broader architectural restructuring is the real need

Inputs

• desired behavior
• target module or slice
• constraints and non-goals
• available test surface

Outputs

• new or updated tests
• minimal implementation
• small refactor if needed
• verification summary

Procedure

1. define the desired behavior in a bounded way
2. add or update tests before implementation
3. make the smallest change that satisfies the tests
4. refactor only inside the declared slice
5. run the tests and record the result
6. report what behavior is now specified and what remains out of scope

Contracts

• behavior should be made explicit before implementation when reasonably possible
• the implementation should stay bounded to the slice
• unrelated refactors should be avoided
• tests should express behavior, not incidental implementation detail

Risks and anti-patterns

• writing tests that merely mirror the implementation
• turning a small slice into a hidden architectural rewrite
• using TDD ritualistically where the problem is not well-shaped yet
• overfitting tests to brittle internal details

Verification

• confirm tests were added or updated first when the task was suitable for TDD
• confirm the implementation stayed bounded
• confirm the relevant test suite passed
• confirm the report names the covered behavior and the untouched behavior

Technique traceability

Manifest-backed techniques:

• AOA-T-0014 from 8Dionysus/aoa-techniques at fe7df9aba3937435b431489ed0f9c5d52690a37c using path techniques/agent-workflows/tdd-slice/TECHNIQUE.md and sections: Intent, When to use, Inputs, Outputs, Core procedure, Contracts, Risks, Validation
• AOA-T-0001 from 8Dionysus/aoa-techniques at fe7df9aba3937435b431489ed0f9c5d52690a37c using path techniques/agent-workflows/plan-diff-apply-verify-report/TECHNIQUE.md and sections: Contracts, Validation

Adaptation points

Project overlays should add:

• local test commands
• local module boundaries
• guidance for when TDD is mandatory versus optional