DELIVER cycle: engineer + reviewer

Overview of the implementation and review loop that constitutes the DELIVER phase.

When to use

This page is not an agent to invoke — it documents the DELIVER loop combining the software-engineer and the software-engineer-reviewer.

Entry contract

Approved BDD scenarios (DISTILL validated)
Architecture decisions (ADRs)

Exit contract

Code implemented, tested, and approved by the reviewer
All artifacts committed

The cycle

graph TB
    SE[software-engineer] -->|implements| CODE[code + tests]
    CODE -->|submits| SER[software-engineer-reviewer]
    SER -->|approve| DONE[✓ DELIVER complete]
    SER -->|reject| SE
    
    style SE fill:#2d5a3d,stroke:#4ed58a
    style SER fill:#3a2d5a,stroke:#8a4ed5
    style DONE fill:#1a3a2d,stroke:#4ed58a

Engineer implements — Walking Skeleton first, then Outside-In TDD (RED → GREEN → REFACTOR)
Reviewer evaluates — 4 independent adversarial lenses
If rejected — The engineer fixes and resubmits (bounded retry)
If approved — The DELIVER phase is complete, artifacts are committed

Invariants

Tests before code — The cycle starts with acceptance tests
Bounded retry — The number of engineer → reviewer cycles is limited
CQS — The engineer writes (command), the reviewer reads (query)
See Customisation for the full list

Why this shape

The RED-GREEN-REFACTOR cycle is the fundamental rhythm of TDD. Each micro-iteration produces a verified increment — not a large batch of untested code.

« The two rules of TDD: write new code only if an automated test has failed; eliminate duplication. » — Beck, K., Test-Driven Development by Example, 2003.

Outside-In TDD starts with the acceptance test (the observable behaviour) and lets internal design emerge from actual needs, not abstract hypotheses.

« Start with an acceptance test that exercises the functionality you want to build. » — Freeman, S. & Pryce, N., Growing Object-Oriented Software, Guided by Tests, 2009.

Allowed customisation

Maximum number of retries (L2)
Mutation score threshold (L2)
Walking Skeleton depth (L2)