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 skills add tamdogood/builder-essential-skills --skill build-scenario-testsgit clone --depth 1 https://github.com/tamdogood/builder-essential-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/tamdogood/builder-essential-skills/build-scenario-tests)<a href="https://agentmods.dev/skills/tamdogood/builder-essential-skills/build-scenario-tests"><img src="https://agentmods.dev/badge/skills/tamdogood/builder-essential-skills/build-scenario-tests/github.svg" alt="Measured on agentmods" height="20"></a>Or the 80×15 button, for a site that already has a row of RSS and ATOM ones. Only the verdict fits; the numbers stay here.
<a href="https://agentmods.dev/skills/tamdogood/builder-essential-skills/build-scenario-tests"><img src="https://agentmods.dev/badge/skills/tamdogood/builder-essential-skills/build-scenario-tests.svg" alt="Reviewed on agentmods" width="80" height="20"></a>- NVIDIA SkillSpector pass
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 | $0.00104 | $0.01331 |
| Opus 5 | $0.00052 | $0.00665 |
| Sonnet 5 | $0.00021 | $0.00266 |
| Haiku 4.5 | $0.00010 | $0.00133 |
Grade A, and why
build-scenario-tests 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 11d 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 — 158 lines — stays where its author put it; the contents beside it link to each section on GitHub.
Build Scenario Tests
Compile one small behavior contract into deterministic, repository-native test code. Understand the host project before choosing a harness, command, fixture, selector, or assertion.
Operating contract
- Treat repository instructions and existing tests as authoritative.
- Keep each scenario focused on one behavior and one reason to fail.
- Compile into the test stack the repository already uses. Add a dependency only when no suitable harness exists and the user accepts the tradeoff.
- Make setup, inputs, actions, and expected results deterministic.
- Prefer public behavior over implementation details. Assert what a user or external caller can observe.
- Keep the Markdown scenario beside the test or in the repository's established specification directory. Record the mapping in both artifacts.
- Never weaken an assertion merely to make a test pass.
Workflow
1. Pass the repository-understanding gate
Read the nearest AGENTS.md or equivalent instructions, product README,
contribution guide, manifests, test configuration, and the smallest relevant
product documentation. Use repository search to find the implementation entry
point, neighboring tests, fixtures, stable selectors, and validation commands.
Trace the relevant action from its public entry point through the state boundary
to the observable result. Do not read the entire tree without a reason.
Before editing, be able to state:
product surface:
behavior source:
relevant architecture and data flow:
runtime or start command:
existing test runner:
nearest tests to imitate:
fixture and state-isolation strategy:
narrow validation command:
full validation command:
known trust or destructive boundaries:
If a material field is unknown, search again. If the repository does not answer it, expose the gap and ask only for the missing product decision. Do not invent commands, selectors, credentials, or expected behavior.
2. Normalize the scenario
Read references/scenario-format.md. If the user provided prose, rewrite it into that contract without changing its intent.
What ships with it
7 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.
- 11d ago First seen · 158 lines · 104 tokens per session scan A d429a1536757
build-scenario-tests is a skill published in the GitHub repository tamdogood/builder-essential-skills (196 stars, last pushed 25d ago), licensed MIT. It adds 104 tokens to every session and 1,331 once invoked, about $0.0005 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.
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