test-engineer

A QA-focused coding agent for planning test suites, writing tests, and checking which parts of code lack coverage.

In plain words
What is it for?
Use it to design unit, integration, or end-to-end tests, add regression tests for bugs, and review test quality or coverage gaps.
Why use it?
It helps you verify code changes systematically and find untested edge cases, errors, and important user flows.

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/junmystery/agent-guidance-python/test-engineer
Clone the repo
git clone --depth 1 https://github.com/JunMystery/Agent-Guidance-Python
Per session 35 Only the description is in the session, so the agent can decide to use it. The body loads when it is invoked.
When invoked 1,526 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 $0.00035 $0.01526
Opus 5 $0.00017 $0.00763
Sonnet 5 $0.00007 $0.00305
Haiku 4.5 $0.00003 $0.00153

Measured yesterday against content hash e279c17e0a25, 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 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.

agents/test-engineer.md · 133 lines

How it starts

The opening of the file, as written. The whole thing — 133 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:

  1. Write a test that demonstrates the bug (must FAIL with current code)
  2. Confirm the test fails
  3. 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

Output Format

When analyzing test coverage:

## Test Coverage Analysis

### Current Coverage
- [X] tests covering [Y] functions/components
- Coverage gaps identified: [list]

### Recommended Tests
1. **[Test name]** — [What it verifies, why it matters]
2. **[Test name]** — [What it verifies, why it matters]

### Priority
- Critical: [Tests that catch potential data loss or security issues]
- High: [Tests for core business logic]
- Medium: [Tests for edge cases and error handling]
- Low: [Tests for utility functions and formatting]

Read the full file on GitHub · 133 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. yesterday First seen · 133 lines · 35 tokens per session scan A e279c17e0a25

Subscribe to this mod's changes

test-engineer is an agent published in the GitHub repository JunMystery/Agent-Guidance-Python (2 stars, last pushed 1mo ago), licensed MIT. It adds 35 tokens to every session and 1,526 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 2026-08-31.

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