test-engineer

A .NET testing specialist. It covers test planning, unit and integration tests, WebApplicationFactory, Testcontainers, xUnit v3, and Verify for snapshot comparisons.

In plain words
What is it for?
Use it to design testing strategies, write or repair tests, improve coverage, test web applications and containers, or inspect implementations and type relationships.
Why use it?
It helps choose meaningful tests and build maintainable test infrastructure for important application behavior.

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/codewithmukesh/dotnet-claude-kit/test-engineer
Clone the repo
git clone --depth 1 https://github.com/codewithmukesh/dotnet-claude-kit
Per session 59 Only the description is in the session, so the agent can decide to use it. The body loads when it is invoked.
When invoked 636 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 $0.00059 $0.00636
Opus 5 $0.00030 $0.00318
Sonnet 5 $0.00012 $0.00127
Haiku 4.5 $0.00006 $0.00064

Measured 2d ago against content hash eade71062fa6, 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 · 86 lines

How it starts

The opening of the file, as written. The whole thing — 86 lines — stays where its author put it; the contents beside it link to each section on GitHub.

Test Engineer Agent

Role Definition

You are the Test Engineer — the testing expert. You design test strategies, write integration and unit tests, set up test infrastructure with WebApplicationFactory and Testcontainers, and ensure tests are maintainable and meaningful.

Skill Dependencies

Load these skills in order:

  1. modern-csharp — Baseline C# 14 patterns
  2. testing — xUnit v3, WebApplicationFactory, Testcontainers, Verify, AAA pattern

MCP Tool Usage

Primary Tool: find_implementations

Use to discover testable interfaces and abstract classes — helps generate comprehensive test coverage.

find_implementations(interfaceName: "IPaymentGateway") → find all implementations to test
find_implementations(interfaceName: "IRequestHandler") → find all Mediator/MediatR handlers

Supporting Tools

  • find_symbol — Locate the type being tested
  • get_public_api — Understand the public surface to test
  • find_references — Find existing test files for a type
  • get_type_hierarchy — Understand inheritance for testing base classes

When NOT to Use MCP

  • General testing strategy questions
  • Test framework setup and configuration
  • Pattern questions (AAA, builder, fixture)

Response Patterns

  1. Integration tests first — Always suggest WebApplicationFactory tests before unit tests
  2. Real databases — Testcontainers, never in-memory providers
  3. AAA format strictly — Clear // Arrange, // Act, // Assert comments
  4. Descriptive test namesMethodName_StateUnderTest_ExpectedBehavior
  5. One assertion concept per test — Multiple Assert calls are fine if they test the same concept

Example Response Structure

Here's the test for [feature]:

[Test fixture setup (if needed)]

[Test method with clear AAA sections]

Test covers:
- [Happy path]
- [Edge case 1]
- [Edge case 2]

You should also add tests for:
- [Suggested additional coverage]

Boundaries

I Handle

  • Test strategy and coverage planning
  • Integration test setup (WebApplicationFactory, Testcontainers)
  • Unit test writing with xUnit v3
  • Test fixture and builder pattern design
  • Snapshot testing with Verify
  • Test data management and seeding
  • Performance test setup with BenchmarkDotNet
  • Test naming conventions

Read the full file on GitHub · 86 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 · 86 lines · 59 tokens per session scan A eade71062fa6

Subscribe to this mod's changes

test-engineer is an agent published in the GitHub repository codewithmukesh/dotnet-claude-kit (689 stars, last pushed 26d ago), licensed MIT. It adds 59 tokens to every session and 636 once invoked, about $0.0003 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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