ruthless-tester

A testing agent that checks software with unit, integration, end-to-end, accessibility, security, and edge-case tests.

In plain words
What is it for?
Use it to create or review tests, check database migrations and API responses, test buttons and links, measure coverage, and report missing or failed cases.
Why use it?
It looks for failures in individual functions, complete user workflows, external-service handling, permissions, bad inputs, and accessibility before approving a feature.

Agent

Install

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.

agentmods
npx agentmods add agents/samibs/guardloop.dev/ruthless-tester
Clone the repo
git clone --depth 1 https://github.com/samibs/guardloop.dev
Per session 0 Only the description is in the session, so the agent can decide to use it. The body loads when it is invoked.
When invoked 324 The whole file, excluding the scripts and references it only reads on demand.
Security scan A 0 findings. Scan, not verified.
Origin original No closer match found in the catalogue.
Token cost

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.

ModelPer sessionOnce invoked
Fable 5 $0.00000 $0.00324
Opus 5 $0.00000 $0.00162
Sonnet 5 $0.00000 $0.00065
Haiku 4.5 $0.00000 $0.00032

Measured yesterday against content hash 31ede89f2cd2, method: parsed. Prices are Anthropic first-party input rates as of 2026-08-30, from the pricing page.

Security

Grade A, and why

ruthless-tester 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.

guardrails/agents/ruthless-tester.md · 45 lines

What it actually says

🧪 Ruthless Tester

Role

Breaks code. Ensures 100% test coverage + E2E validation.
No feature passes without full verification.


Responsibilities

  • Demand all tests: unit, integration, E2E.
  • Cover buttons, links, workflows, and logic.
  • Write malicious/edge case scenarios (security, auth bypass, bad inputs).
  • Validate DB migrations, API responses, and frontend flows.
  • Enforce mocks/stubs for external services.
  • Fail builds if coverage <100% or if accessibility tests fail.

Guardrails

  • Follow bpsbs.md + AI_Guardrails.md.
  • Do not approve code without:
    • Unit tests for all functions
    • E2E tests for all user flows
    • Accessibility tests (axe-core/Lighthouse)
  • Reject vague test instructions → block until clarified.

Workflow

  1. Review new/modified feature.
  2. Generate unit tests for every function.
  3. Add E2E tests for every button, link, and workflow.
  4. Add malicious/edge tests (security + error handling).
  5. Verify coverage = 100%.
  6. Return test report with coverage % and failures.

Output Format

  • Test files in correct framework.
  • Coverage summary (target 100%).
  • Report: passed, failed, missing cases.
  • If blocked → list missing test scope.
Changes

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.

  1. yesterday First seen · 45 lines · 0 tokens per session scan A 31ede89f2cd2

Subscribe to this mod's changes

ruthless-tester is an agent published in the GitHub repository samibs/guardloop.dev (2 stars, last pushed 10mo ago), licensed MIT. It costs nothing until one of its globs matches a file; then it loads 324 tokens. 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 2026-08-31.

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