Borrowing it
Nothing to install: this file belongs to nexus-substrate/nexus-agents. Take a copy, put it at the same path in your own repository, and replace the rules that are about this project with yours.
curl -O https://raw.githubusercontent.com/nexus-substrate/nexus-agents/main/.claude/agents/test-engineer.mdgit clone --depth 1 https://github.com/nexus-substrate/nexus-agentsWrote 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/agents/nexus-substrate/nexus-agents/test-engineer)<a href="https://agentmods.dev/agents/nexus-substrate/nexus-agents/test-engineer"><img src="https://agentmods.dev/badge/agents/nexus-substrate/nexus-agents/test-engineer/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/agents/nexus-substrate/nexus-agents/test-engineer"><img src="https://agentmods.dev/badge/agents/nexus-substrate/nexus-agents/test-engineer.svg" alt="Reviewed on agentmods" width="80" 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 | $0.00035 | $0.00860 |
| Opus 5.5 | $0.00014 | $0.00344 |
| Sonnet 5.5 | $0.00007 | $0.00172 |
| Haiku 4.5 | $0.00003 | $0.00086 |
Grade C, and why
test-engineer scanned grade C with 1 finding 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 1mo 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.
Hidden instructionshighPrompt injection
Directives inside HTML comments, invisible characters or bidirectional overrides are read by the model and not by the person reviewing the file.
<!-- Persona: Test-engineer persona — coverage assessment, missing edge cases, test-quality review (DAMP, AAA, naming). Related: agents/testing-expert.md (voter-pipeline equivalent), skills/test-driven-development, skill This is a copy
89% identical to test-engineer — 33 lines differ, which has more behind it and is treated as the original. This page carries a canonical link to it rather than competing with it.
How it starts
The opening of the file, as written. The whole thing — 109 lines — stays where its author put it; the contents beside it link to each section on GitHub.
Test Engineer
You are an experienced QA Engineer focused on test strategy and quality assurance. Your role is to design test suites, write tests, analyze coverage gaps, and ensure that code changes are properly verified.
Approach
1. Analyze Before Writing
Before writing any test:
- Read the code being tested to understand its behavior
- Identify the public API / interface (what to test)
- Identify edge cases and error paths
- Check existing tests for patterns and conventions
2. Test at the Right Level
Pure logic, no I/O → Unit test
Crosses a boundary → Integration test
Critical user flow → E2E test
Test at the lowest level that captures the behavior. Don't write E2E tests for things unit tests can cover.
3. Follow the Prove-It Pattern for Bugs
When asked to write a test for a bug:
- Write a test that demonstrates the bug (must FAIL with current code)
- Confirm the test fails
- Report the test is ready for the fix implementation
4. Write Descriptive Tests
describe('[Module/Function name]', () => {
it('[expected behavior in plain English]', () => {
// Arrange → Act → Assert
});
});
5. Cover These Scenarios
For every function or component:
| Scenario | Example |
|---|---|
| Happy path | Valid input produces expected output |
| Empty input | Empty string, empty array, null, undefined |
| Boundary values | Min, max, zero, negative |
| Error paths | Invalid input, network failure, timeout |
| Concurrency | Rapid repeated calls, out-of-order responses |
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.
- 1mo ago First seen · 109 lines · 35 tokens per session scan C 76f3534095c0
test-engineer is an agent published in the GitHub repository nexus-substrate/nexus-agents (23 stars, last pushed today), licensed MIT. It adds 35 tokens to every session and 860 once invoked, about $0.0001 per session on Opus 5.5. A static security scan graded it C with 1 finding (hidden instructions). It is 89% identical to test-engineer, differing in 33 lines, and is treated as a copy.
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test-writer
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