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/aneja5/forge-skills/tddnpx skills add aneja5/forge-skills --skill tddgit clone --depth 1 https://github.com/aneja5/forge-skillsWrote this? Show the measurements
A badge with what this costs and how it scanned, read live from this page, so it follows the numbers instead of freezing them. Markdown for a README, HTML for a documentation site or a project page.
[](https://agentmods.dev/skills/aneja5/forge-skills/tdd)<a href="https://agentmods.dev/skills/aneja5/forge-skills/tdd"><img src="https://agentmods.dev/badge/skills/aneja5/forge-skills/tdd.svg" alt="Measured on agentmods" height="20"></a>What 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 5.1 | $0.00056 | $0.01801 |
| Opus 5 | $0.00028 | $0.00901 |
| Sonnet 5 | $0.00011 | $0.00360 |
| Haiku 4.5 | $0.00006 | $0.00180 |
Grade A, and why
tdd 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 2d 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 — 157 lines — stays where its author put it; the contents beside it link to each section on GitHub.
Test-Driven Development
Overview
Tests verify behavior through public interfaces, not implementation details. One failing test → minimum code to pass → repeat. Never write all tests first. See tests.md for examples and mocking.md for mocking guidelines.
When to Use
- Implementing a task from
.forge/tasks.yamlthat needs test-first discipline - Any feature or bug fix where behavior must be proven before merging
- User explicitly asks for TDD or red-green-refactor
When NOT to Use
- Writing tests retroactively for already-working code — that's a different activity
- Exploratory spike to understand a problem space — spike first, then TDD the result
- Config changes with no behavioral assertions possible
Common Rationalizations
| Thought | Reality |
|---|---|
| "I'll write tests after the implementation works" | Then you test implementation shape, not behavior |
| "Writing all tests first is TDD" | That's horizontal slicing — produces brittle tests |
| "This behavior is obvious, no test needed" | Obvious behaviors are the ones that silently break |
| "I need to mock my own modules to test this" | Your interface boundaries need rethinking |
| "The test is too hard to write" | The interface is too hard to use — fix the interface |
Red Flags
- Test names describe HOW not WHAT ("calls paymentService.process")
- Test mocks internal collaborators owned by the same codebase
- Test breaks on refactor when behavior didn't change
- All tests written before any implementation ("horizontal slicing")
- Test verifies through side effects or database state instead of interface
.forge/testing-strategy.mdexists but was not read before writing the first test (its per-module coverage decisions override TDD defaults)
Precedence with testing-strategy
If .forge/testing-strategy.md exists, read it first. It is the authoritative source for per-module test policy. TDD's default is "every behavior gets a test"; the strategy may carve exceptions:
What ships with it
5 files beside SKILL.md in the same directory: the scripts, references and assets a skill reads on demand. Not counted in the per-session cost; read them before you install if any of them is executable.
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.
- 2d ago First seen · 157 lines · 56 tokens per session scan A bc6f9666a4f2
tdd is a skill published in the GitHub repository aneja5/forge-skills (3 stars, last pushed 3mo ago), licensed MIT. It adds 56 tokens to every session and 1,801 once invoked, about $0.0003 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 2026-09-03.
Other skills, from other repositories
tdd
Use when implementing features or bug fixes test-first.
link-ticket-to-session
Link the current Claude Code session to a ticket (Linear, Jira, GitHub Issues, or GitHub Pull Requests) and cache its title/status in karma. Use when the user explicitly asks to link, attach, associate, or connect this session to a ticket, issue, or PR — e.g. "/link-ticket-to-session ABC-123", "link this session to…
auto-loop
TDD-based autonomous development loop with checkpoint recovery and observability changelog.
workflow
Run the complete 5-step development workflow: focus problem → prevent over-development → test-first (TDD) → document → smart commit. Use when starting a new feature, or when the user runs /workflow or asks for the full development flow.
test-first
Drive one feature through a strict TDD Red-Green-Refactor cycle with checklists for each phase. Use when implementing new functionality test-first, or when the user runs /test-first.
test-audit
Audit test suites for T1-T4 violations using AST analysis, mock detection, and multi-stage synthesis. Invoke when user asks to audit tests, check test quality, find mock violations, review test effectiveness, or inspect test suites for over-mocking. Triggers automatic rewrites when quality gates fail.