test-driven-development

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• SKILL.md

SKILL.md (first lines)

# Execute

→ False-positive entry on a native-direct-skill host? → **Exit immediately unless the user explicitly asked for TDD or the conversation already contains `TDD Route: strict`.**
  In `off` mode, do not start RED / GREEN / REFACTOR from generic bugfix, contract, shared-module, or risky-code wording alone.
  Hand control back to `using-aegis`, `systematic-debugging`, `writing-plans`, or the fast path with verification.
→ Implementing a feature or bugfix under TDD Route `strict`? → **No production code without a failing test first.**
  Gate: medium/high complexity? → route to brainstorming or writing-plans first.
  Mode: default `off` disables automatic TDD, not completion verification; `auto` chooses strict/light/skipped by risk.
  Change Necessity: before strict RED/GREEN enters production edits, confirm the slice really needs a code change.
  Cycle: RED (write test → watch it fail) → GREEN (minimal code → watch it pass) → REFACTOR (clean up → keep green)
  Regression: shared module → related tests. contract change → producer + consumer. core logic → old + new tests.
  Ripple signal hit → cover producer+consumer or real user path before claiming green.
  GREEN proves the currently expressed behavior slice only.
  GREEN does not by itself prove parent-task acceptance, business-value completion, or final completion.
→ Done when: chosen TDD Route is recorded, strict-route tests pass, TDD preflight gate passed when applicable, pre-edit complexity risk was checked for non-trivial source edits, and `verification-before-completion` has fresh evidence.

# Test-Driven Development (TDD)

## Overview

Under `TDD Route: strict`, write the test first. Watch it fail. Write minimal
code to pass.

If you didn't watch the test fail, you don't know if it tests the right thing.

TDD Mode has two values: `off` and `auto`. The default `off` mode disables
automatic TDD routing but never disables `verification-before-completion`.
`auto` lets Aegis choose a `TDD Route` by task risk.

On native-direct-skill hosts, automatic entry must stay anchored to literal
conversation markers such as `TDD Route: strict`, `strict TDD`, `test-first`,
or `RED / GREEN / REFACTOR`, not generic risky-implementation wording.

## When to Use

Only enter this skill after one of these explicit entry signals exists:

- the user explicitly asks for strict TDD, test-first development, or RED / GREEN / REFACTOR
- the current conversation already contains `TDD Route: strict` from another Aegis workflow

Typical strict-route shapes once entry is already justified: new features, bug
fixes, refactoring, behavior or logic changes, interface/data contract changes,
cross-module or shared-module changes, and core logic refactors.

Exceptions (ask your human partner): throwaway prototypes, generated code, config files, pure docs cleanup, read-only diagnosis, comment-only changes.

## TDD Mode and Route

Before source edits, decide:

```text
Aegis Visibility:
- Why this TDD route is strict, light, or skipped:
- What RED/GREEN proves:
- What still needs verification:

TDD Route:
- Mode: auto | off
- Decision: strict | light | skipped
- Strict authority: explicit user/project request | recorded auto decision | not applicable
- Test posture: diagnostic reproduction | post-change regression | strict RED test
- Reason:
- Verification:
```

In `auto`, use `strict` for behavior, bugfix, contract, shared/core, producer /
consumer, persistence, permission, migration, or meaningful regression risk.
Use `light` for tiny low-risk edits with an obvious readback or command check.
Use `skipped` for read-only, docs-only, generated, throwaway, comment-only, or
environment-bound work where TDD does not fit.

In `off`, do not automatically require TDD, create a strict route, or infer one
from risk alone. Explicit user/project TDD requests still apply; risky work may
still need regression coverage and `verification-before-completion` before any
completion claim.
For plan or execution review, `Mode: off / Decision: skipped` is the normal
record unless an explicit user/project strict request overrides it. That record
does not load this skill or turn a diagnostic reproduction into RED. An
approved plan does not supply strict authority by itself.
If this skill was loaded anyway without an explicit TDD request or a visible
`TDD Route: strict` marker, exit instead of improvising an automatic strict
route from risk words alone.

Keep `Aegis Visibility` task-specific: explain the route decision and the
regression boundary, not a generic claim that TDD was used.

## Preflight Gate

TDD is the implementation discipline for an approved behavior or atomic task.
It is not a substitute for task routing, product clarification, or planning.

Before writing tests or production code, stop and route to brainstorming or
writing-plans if the current request has any medium- or high-complexity signal:

- multiple files, modules, pages, screens, services, or owners
- user-visible flows such as navigation, onboarding, checkout, lifecycle, or
  recovery paths
- state transitions, routing rules, API or data contracts, compatibility
  boundaries, migrations, permissions, or persistence
- more than one acceptance path or manual/visual verification requirement
- unclear product behavior, competing constraints, or long-running execution

For these tasks, require a baseline read-set, plan, and atomic tasks before TDD.
High-complexity or ambiguous tasks also need a spec/design review before
planning. Only proceed directly with TDD for low-complexity work whose intent,
owner, compatibility boundary, verification path, and slice goal / success
evidence are already clear.

## Change Necessity

Before strict RED/GREEN enters production code edits, make the code-change
decision visible. Any new source-code path needs this check before RED/GREEN
normalizes it as work to implement. This is the "should code change at all?"
check; it is not a new artifact and does not belong in the `using-aegis` hot
path.

This is behavior-triggered, not prompt-triggered. If strict TDD is about to add
any new source-code path or enter production source edits, expose a natural
readback even when the user did not ask for it. A tiny helper, small guard, new

From GanyuanRan/Aegis, MIT.

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