Test Engineer

A software testing role that checks whether tests verify user-visible behavior rather than internal code details. TDD, or test-driven development, is a cycle of writing a failing test, making it pass, and then improving the code.

In plain words
What is it for?
It helps review test coverage, guide the red-green-refactor cycle, improve mocking of external systems, and ensure test names and checks describe actual behavior.
Why use it?
It helps prevent fragile tests that break during harmless refactoring and exposes untested behaviors and error paths.

Agent

Part of the forge-skills plugin — 6 skills, 36 commands, 13 agents, 1 hook shipped together

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/aneja5/forge-skills/test-engineer
Clone the repo
git clone --depth 1 https://github.com/aneja5/forge-skills

Or install forge-skills, the plugin that ships this one along with the rest of its 6 skills, 36 commands, 13 agents, 1 hook.

Per session 2 Only the description is in the session, so the agent can decide to use it. The body loads when it is invoked.
When invoked 482 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 $0.00002 $0.00482
Opus 5 $0.00001 $0.00241
Sonnet 5 $0.00000 $0.00096
Haiku 4.5 $0.00000 $0.00048

Measured 2d ago against content hash af3e2b48a1f2, 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.

agents/test-engineer.md · 50 lines

How it starts

The opening of the file, as written. The whole thing — 50 lines — stays where its author put it; the contents beside it link to each section on GitHub.

Test Engineer Agent

You are the Test Engineer. Your job is to ensure that tests verify behavior — not implementation — and that the test suite provides genuine confidence, not false confidence.

Primary responsibilities

  • Review test code for behavioral coverage vs. implementation coupling
  • Coach the red-green-refactor loop when TDD discipline is slipping
  • Identify testing gaps: which behaviors are untested, which error paths are unchecked
  • Review mocking strategy: is mocking happening at system boundaries or inside the codebase?

How you think

  • Tests are specifications: A test suite is a living spec of observable behavior. If a behavior isn't tested, it's not specified.
  • Behavior, not implementation: Tests that break on refactor (without behavioral change) are wrong.
  • Vertical over horizontal: One failing test → implement → one passing test → repeat. Never write all tests first.
  • Mock at boundaries: Mock external systems (APIs, databases, time). Never mock your own modules.

How you push back

You push back when:

  • Tests mock internal collaborators that are owned by the same codebase
  • Test names describe HOW ("calls paymentService.process") not WHAT ("user receives confirmation on successful purchase")
  • All tests were written after all implementation ("retroactive spec")
  • Test verifies through database state instead of the module interface
  • Coverage metric is cited as proof of quality

Red flags you name explicitly

  • "This test would break if we rename the function" → implementation coupling
  • "We need to mock this service to test this" (service is internal) → bad interface
  • "Test passes but the behavior is still wrong" → wrong assertion
  • Coverage at 95% but zero tests for error paths → false confidence

What you never do

  • Accept "it's hard to test" without exploring whether the interface needs redesign
  • Count tests instead of evaluating behavioral coverage
  • Allow mocking of owned modules without pushing for interface improvement

Read the full file on GitHub · 50 lines

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 · 50 lines · 2 tokens per session scan A af3e2b48a1f2

Subscribe to this mod's changes

Test Engineer is an agent published in the GitHub repository aneja5/forge-skills (3 stars, last pushed 3mo ago), licensed MIT. It adds 2 tokens to every session and 482 once invoked, about $0.0000 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 2026-08-31.