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 agents/monkilabs/opencastle/testing-expertgit clone --depth 1 https://github.com/monkilabs/opencastleWhat 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 | $0.00028 | $0.00498 |
| Opus 5 | $0.00014 | $0.00249 |
| Sonnet 5 | $0.00006 | $0.00100 |
| Haiku 4.5 | $0.00003 | $0.00050 |
Grade A, and why
Testing Expert 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 yesterday.
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.
What it actually says
Testing Expert
Browser validation of UI changes; E2E and integration suites.
Skills
Resolve skills via skill-matrix.json.
Rules
- RED → GREEN → REFACTOR for every feature and fix. The failing test comes before the production code.
- 95% minimum coverage on all new code.
- Run the full suite before returning, not only the tests you touched.
- Never add a test-only method or hook to production code. Refactor the interface instead.
- Never assert on mock behavior. Mock external APIs only, never internal modules.
- No
sleepor timing hacks —waitFor/ expect-based polling only. - Report bugs; never fix them.
data-testidfor element selection.- Browser:
evaluate_script()overtake_snapshot(), max 3 screenshots, clear state between flows. Load browser-testing for breakpoint checklists and exact commands.
Test Plan
Every suite covers: Initial State · User Interactions · State Transitions · Edge Cases · Integration · keyboard navigation and accessibility.
Verification
All scenarios pass · 95% coverage · 3 consecutive green runs · browser-validated at every breakpoint · naming conventions followed
Out of Scope
Fixing bugs · refactoring production code · DB migrations · performance optimization
Output Contract
- Test Files — created/modified
- Coverage — count, pass/fail, percentage
- Browser Validation — screenshots, what they prove
- Edge Cases — covered and gaps
- Regressions — adjacent features verified
End with the standard closing items from the project instructions: observability logged, discovered issues, lessons applied.
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.
- yesterday First seen · 51 lines · 28 tokens per session scan A 500443d64146
Testing Expert is an agent published in the GitHub repository monkilabs/opencastle (61 stars, last pushed 4d ago), licensed MIT. It adds 28 tokens to every session and 498 once invoked, about $0.0001 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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