Getting it into your agent
One page per mod, every tool's command on it. A separate URL per tool would split the same page into five that compete with each other.
npx agentmods add skills/nexus-substrate/nexus-agents/test-driven-developmentnpx skills add nexus-substrate/nexus-agents --skill test-driven-developmentgit clone --depth 1 https://github.com/nexus-substrate/nexus-agentsWhat it costs to keep this loaded
Counted locally with the o200k_base tokenizer, which is exact for GPT models; Claude uses its own tokenizer and its counts differ. Treat this as one consistent yardstick across the catalogue rather than a bill. Prices are per million input tokens.
| Model | Per session | Once invoked |
|---|---|---|
| Fable 5 | $0.00089 | $0.01386 |
| Opus 5 | $0.00044 | $0.00693 |
| Sonnet 5 | $0.00018 | $0.00277 |
| Haiku 4.5 | $0.00009 | $0.00139 |
Grade A, and why
test-driven-development scanned grade A with 0 findings against 26 rules in 11 categories — prompt injection, anti-refusal, data exfiltration, privilege escalation, supply chain, agent snooping, system-prompt leakage, SSRF and excessive agency — measured 3d ago.
A static scan of the body, not an audit. Every finding is printed with the line that produced it so you can judge whether it matters here. A mod is markdown that instructs an agent; that is exactly why what it instructs is worth reading.
Nothing flagged
None of the 26 patterns this scan looks for appear in this file: no shell pipes, no recursive deletes, no credential paths, no hidden text, no instruction-override or anti-refusal phrasing, no agent-config snooping. That is not a guarantee, it is the absence of the things that are checkable.
How it starts
The opening of the file, as written. The whole thing — 106 lines — stays where its author put it; the contents beside it link to each section on GitHub.
Test-Driven Development Skill
Full workflow: CONTRIBUTION_GUIDE.md. Prime directive: CLAUDE.md → Development Disciplines.
When to apply
- Any new logic or behavior — write the test first
- Bug fixes — use the Prove-It Pattern (failing test demonstrates the bug, then fix)
- Modifications to existing functionality
- Edge cases and error paths
- Any change that risks regressing tested behavior
Skip TDD for:
- Configuration-only edits (pure values, no branching)
- Documentation changes
- Static asset moves with no behavioral impact
The Red-Green-Refactor cycle
- RED — write a test that fails because the functionality doesn't exist yet. Run it. Confirm the failure message points at the missing piece.
- GREEN — implement the minimum code to make the test pass. Resist the urge to "round out" the API in the same step.
- REFACTOR — improve names, structure, duplication while keeping the test green. Run the suite after every refactor step.
The Prove-It Pattern (bug fixes)
When a bug is reported:
- Reproduce the bug with a minimal failing test.
- Confirm the test fails in
main— this proves the bug exists and your test is correctly sensitive. - Implement the fix at the root cause (see
bug-fixskill for triage layering). - Confirm the test now passes.
- Run the full suite —
pnpm test— to catch regressions the fix may have introduced elsewhere.
The test stays as a regression guard. Future refactors can't silently re-break this case.
Test pyramid (target shape)
| Tier | Share | Latency | Scope |
|---|---|---|---|
| Unit | ~80% | milliseconds | single module, no I/O |
| Integration | ~15% | seconds | component interactions, may touch fs/db |
| E2E | ~5% | minutes | critical user flows end-to-end |
What this file has done since we first saw it
Hashed on every crawl. A supply-chain change to an agent config is a question of when, not whether, so the history is kept rather than the latest state alone.
- 3d ago First seen · 106 lines · 89 tokens per session scan A 57378c145537
test-driven-development is a skill published in the GitHub repository nexus-substrate/nexus-agents (18 stars, last pushed 2d ago), licensed MIT. It adds 89 tokens to every session and 1,386 once invoked, about $0.0004 per session on Opus 5. A static security scan graded it A with 0 findings. No closer match exists in the catalogue, so it is treated as the original; first seen 2026-08-30.
Other skills, from other repositories
agent-integration
Run all three agent integration phases sequentially: research, write-tests, and implement using E2E-first TDD (unit tests written last). For individual phases, use /agent-integration:research, /agent-integration:write-tests, or /agent-integration:implement. Use when the user says "integrate agent", "add agent…
engram-testing-coverage
TDD and coverage standards for Engram. Trigger: When implementing behavior changes in any package.
code-assist
Guides implementation of code tasks using test-driven development in an Explore, Plan, Code, Commit workflow. Acts as a Technical Implementation Partner and TDD Coach — following existing patterns, avoiding over-engineering, and producing idiomatic, modern code.
tdd
Test-driven development. Use when the user wants to build features or fix bugs test-first, mentions "red-green-refactor", or wants integration tests.
css-design-tdd
Test-driven CSS design system modifications. Run checks before/after CSS changes to verify token usage, variable definitions, fallbacks, and consistency. Use when modifying CSS tokens, fixing design inconsistencies, or auditing CSS architecture.
mobiai-mobile-tdd
You MUST use this before writing any implementation code for a mobile feature, bug fix, refactor, or behavior change. Tests come before implementation — no exceptions.