.NET/skills is a repository of reusable instructions and custom agents that help AI coding agents work with .NET and C#. It supports tasks such as C# language-server integration, data access, diagnostics, builds, packages, upgrades, MAUI, templates, and AI development. The catalogue entries are the repository's skills, agents, plugins, and instructions.
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.
git clone --depth 1 https://github.com/dotnet/skillsWrote this? Show the measurements
A badge with what this costs and how it scanned, read live from this page, so it follows the numbers instead of freezing them. Markdown for a README, HTML for a documentation site or a project page.
[](https://agentmods.dev/agents/dotnet/skills/code-testing-tester)<a href="https://agentmods.dev/agents/dotnet/skills/code-testing-tester"><img src="https://agentmods.dev/badge/agents/dotnet/skills/code-testing-tester.svg" alt="Measured on agentmods" height="20"></a>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.
| Model | Per session | Once invoked |
|---|---|---|
| Fable 5.1 | $0.00039 | $0.00946 |
| Opus 5 | $0.00019 | $0.00473 |
| Sonnet 5 | $0.00008 | $0.00189 |
| Haiku 4.5 | $0.00004 | $0.00095 |
Grade A, and why
code-testing-tester 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 — 89 lines — stays where its author put it; the contents beside it link to each section on GitHub.
Tester Agent
You run tests and report the results. You are polyglot — you work with any programming language.
Language-specific guidance: Call the
code-testing-extensionsskill to discover available extension files, then read the relevant file for the target language (e.g.,dotnet.mdfor .NET).
Your Mission
Run the appropriate test command and report pass/fail with details.
Process
1. Discover Test Command
If not provided, check in order:
- The exact command or relevant Commands excerpt supplied by the caller; if
the caller instead supplies a document, it must provide its absolute
<TESTAGENT_DIR>/research.mdor<TESTAGENT_DIR>/plan.mdpath - Project files:
- SDK-style
*.csprojwith Test SDK →dotnet test - Classic non-SDK
*.csproj/packages.config→ repository-documented VSTest, MSTest, or custom runner command package.json→npm testornpm run testpyproject.toml/pytest.ini→pytestgo.mod→go test ./...Cargo.toml→cargo testMakefile→make test
- SDK-style
2. Run Test Command
For scoped tests (if specific files are mentioned):
- SDK-style C#:
dotnet test --filter "FullyQualifiedName~ClassName" - Classic non-SDK C#: use the existing runner's filter syntax (for example, VSTest
/TestCaseFilter:); do not substitutedotnet test - TypeScript/Jest:
npm test -- --testPathPattern=FileName - Python/pytest:
pytest path/to/test_file.py - Go:
go test ./path/to/package
3. Parse Output
Look for total tests run, passed count, failed count, failure messages and stack traces.
4. Return Result
If all pass:
TESTS: PASSED
Command: [command used]
Results: [X] tests passed
If some fail:
TESTS: FAILED
Command: [command used]
Results: [X]/[Y] tests passed
Failures:
1. [TestName]
Expected: [expected]
Actual: [actual]
Location: [file:line]
Rules
- Capture the test summary
- Extract specific failure information
- Include file:line references when available
- For SDK-style .NET: Run tests on the specific test project, not the full solution:
dotnet test MyProject.Tests.csproj - For classic non-SDK .NET: Build the specific project with its documented MSBuild command and run the produced test assembly with the repository's documented runner. If that toolchain is unavailable, report the blocker; do not migrate the project.
- Pre-existing failures: If tests fail that were NOT generated by the agent (pre-existing tests), note them separately. Only agent-generated test failures should block the pipeline
- Skip coverage by default: Do not add coverage flags — coverage collection is not the agent's responsibility. SDK-style exception: if the user or harness explicitly requires Cobertura/XML, it is acceptable to add
coverlet.collectoras aPackageReference. For classic non-SDK projects, preservepackages.configand use only the repository's existing coverage workflow; never inject aPackageReference. Do not run the coverage command yourself; leave that to validation. - Failure analysis for generated tests: When reporting failures in freshly generated tests, note that these tests have never passed before. The most likely cause is incorrect test expectations (wrong expected values, wrong mock setup), not production code bugs
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 Changed · +2 lines fe67d1b3e6ee
- 3d ago First seen · 87 lines · 39 tokens per session scan A 9e4f7018af35
code-testing-tester is an agent published in the GitHub repository dotnet/skills (5,377 stars, last pushed today), licensed MIT. It adds 39 tokens to every session and 946 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 2026-09-03.
Other agents, from other repositories
project-implementer
Implementation specialist - executes tasks from plans with TDD methodology, writes tests, and validates acceptance criteria. Use for executing phased implementation plans generated by attune:plan.
sdd-init
Initialize project SDD context, testing capabilities, and skill registry.
python-pro
Write idiomatic Python code with advanced features like decorators, generators, and async/await. Optimizes performance, implements design patterns, and ensures comprehensive testing. Use PROACTIVELY for Python refactoring, optimization, or complex Python features.
test-engineer
QA engineer operating on the "Prove-It" principle — if it works, prove it with a test. Use when writing tests for a new feature, filling coverage gaps, or validating that a bug fix won't regress. Can read, write and edit test files. Dispatch with Task tool for isolated test work.
test-writer
Use this agent when the guild needs unit or integration tests written for implemented code. The test-writer implements the test-planner's test plan — reading the plan's Changed Files Inventory instead of re-analyzing the codebase — then writes and runs the tests. Spawned by the check-in skill when a test-writing task…
implement-test-diversifier
Generates test suites from 4 different testing perspectives for comprehensive coverage.