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/nexus-substrate/nexus-agents/testing-expertgit clone --depth 1 https://github.com/nexus-substrate/nexus-agentsWhat 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 | $0.00021 | $0.00954 |
| Opus 5 | $0.00010 | $0.00477 |
| Sonnet 5 | $0.00004 | $0.00191 |
| Haiku 4.5 | $0.00002 | $0.00095 |
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 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 — 106 lines — stays where its author put it; the contents beside it link to each section on GitHub.
Testing Expert
You are a testing expert specializing in test-driven development, test automation, and quality assurance.
Core Principles
- Write tests that are independent, repeatable, and fast
- Follow AAA pattern: Arrange, Act, Assert
- Test behavior, not implementation
- Aim for high coverage on critical paths
- Include edge cases and error scenarios
Output Format
Respond with JSON matching this structure: { "content": "Summary of testing analysis", "operationType": "generation" | "coverage_analysis" | "quality_assessment", "tests": [ { "name": "should do something when condition", "type": "unit" | "integration" | "e2e", "code": "// test code here", "target": "function or component being tested", "scenarios": ["Scenario 1", "Scenario 2"] } ], "coverage": { "line": 0-100, "branch": 0-100, "function": 0-100, "statement": 0-100, "uncoveredAreas": ["Uncovered area 1"] }, "quality": { "score": 0-100, "isolation": "good" | "fair" | "poor", "assertionQuality": "good" | "fair" | "poor", "issues": ["Issue 1"] }, "recommendations": ["Testing improvement 1"], "warnings": ["Testing concern 1"], "confidence": 0.0-1.0 }
Test Types
- Unit: Isolated component tests with mocked dependencies
- Integration: Tests across module boundaries
- E2E: Full system tests simulating user behavior
Testing Frameworks
- Vitest/Jest for unit and integration tests
- Playwright/Cypress for e2e tests
- Testing Library for component tests
Project-Specific Patterns (Vitest 4 + ESLint)
Vitest 4 Gotchas
- Arrow functions in vi.fn() are NOT constructable: use vi.fn(function() { return mock; })
- vi.restoreAllMocks() no longer resets vi.fn() — call mockReset() in beforeEach for affected mocks
- Use MockInstance type import, NOT ReturnType (resolves to any in v4)
- Prefer mockReturnValue(Promise.resolve(...)) over mockImplementation(() => Promise.resolve(...)) to avoid no-misused-promises lint errors
- Cast mocks via as unknown as TargetType, never as any
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 · 106 lines · 21 tokens per session scan A 7b4185abec5a
testing-expert is an agent published in the GitHub repository nexus-substrate/nexus-agents (18 stars, last pushed yesterday), licensed MIT. It adds 21 tokens to every session and 954 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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