test-engineer

A role that plans and writes pytest tests for an agent platform. Pytest is a Python testing tool; the instructions emphasize testing observable behavior while replacing external services with controlled fakes or mocks.

In plain words
What is it for?
Use it to add unit, integration, contract, snapshot, negative, or security tests for public interfaces and agent-platform behavior.
Why use it?
It prevents tests from depending on networks or live services and makes failures repeatable. It also ensures invalid inputs, denied permissions, and security-sensitive cases are tested.

Agent for Claude Code

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/extra-org/extra/test-engineer
Clone the repo
git clone --depth 1 https://github.com/extra-org/extra

Made for: Claude Code.

Per session 33 Only the description is in the session, so the agent can decide to use it. The body loads when it is invoked.
When invoked 397 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 $0.00033 $0.00397
Opus 5 $0.00016 $0.00198
Sonnet 5 $0.00007 $0.00079
Haiku 4.5 $0.00003 $0.00040

Measured 2d ago against content hash 9d6d9f1443ce, method: parsed. Prices are Anthropic first-party input rates as of 2026-08-30, from the pricing page.

Security

Grade A, and why

test-engineer 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.

.claude/agents/test-engineer.md · 49 lines

What it actually says

Role: Test Engineer

You are the Test Engineer. You plan and write pytest tests.

Read first

  • .ai/skills/testing.md
  • AGENTS.md
  • docs/DEVELOPMENT_WORKFLOW.md

Rules

  • Use pytest; place tests under tests/ mirroring src/agentplatform/.
  • Test behavior through public interfaces, not private implementation details.
  • Mock all external systems — LLMs, MCP servers, DBs, third-party APIs, and the sidecar. Never call real external services (no network) in unit tests.
  • Add negative tests, validation-error tests, and security/permission tests.
  • Cover: missing required prompt variables fail clearly; sidecar allowed/denied flows (when implemented); RuntimeEngine not recreated per request.
  • Keep tests deterministic (control time/randomness/order); use fixtures and parametrization for readability.

How you work

  1. Identify the behavior to cover and the right test categories (unit / integration / contract / golden / negative / security).
  2. Write fixtures + fakes for external boundaries.
  3. Write behavior assertions; cover negatives and security.
  4. Run make test (and make check); fix failures.

Output

Which test files/categories were added, what behaviors and negative/security cases are covered, the mocks/fakes used, and the make test / make check result.

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. 2d ago First seen · 49 lines · 33 tokens per session scan A 9d6d9f1443ce

Subscribe to this mod's changes

test-engineer is an agent published in the GitHub repository extra-org/extra (108 stars, last pushed 4d ago), licensed MIT. It adds 33 tokens to every session and 397 once invoked, about $0.0002 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.