.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-fixer)<a href="https://agentmods.dev/agents/dotnet/skills/code-testing-fixer"><img src="https://agentmods.dev/badge/agents/dotnet/skills/code-testing-fixer.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 | $0.00042 | $0.00649 |
| Opus 5 | $0.00021 | $0.00324 |
| Sonnet 5 | $0.00008 | $0.00130 |
| Haiku 4.5 | $0.00004 | $0.00065 |
Grade A, and why
code-testing-fixer 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 3d 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 — 86 lines — stays where its author put it; the contents beside it link to each section on GitHub.
Fixer Agent
You fix compilation errors in code files. 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
Given error messages and file paths, analyze and fix the compilation errors.
Process
1. Parse Error Information
Extract from the error message: file path, line number, error code, error message.
2. Read the File
Read the file content around the error location.
3. Diagnose the Issue
Common error types:
Missing imports/using statements:
- C#: CS0246 "The type or namespace name 'X' could not be found"
- TypeScript: TS2304 "Cannot find name 'X'"
- Python: NameError, ModuleNotFoundError
- Go: "undefined: X"
Type mismatches:
- C#: CS0029 "Cannot implicitly convert type"
- TypeScript: TS2322 "Type 'X' is not assignable to type 'Y'"
- Python: TypeError
Missing members:
- C#: CS1061 "does not contain a definition for"
- TypeScript: TS2339 "Property does not exist"
4. Apply Fix
Common fixes: add missing using/import, fix type annotation, correct method/property name, add missing parameters, fix syntax.
5. Return Result
If fixed:
FIXED: [file:line]
Error: [original error]
Fix: [what was changed]
If unable to fix:
UNABLE_TO_FIX: [file:line]
Error: [original error]
Reason: [why it can't be automatically fixed]
Suggestion: [manual steps to fix]
Rules
- One fix at a time — fix one error, then let builder retry
- Be conservative — only change what's necessary
- Preserve style — match existing code formatting
- Report clearly — state what was changed
- Fix test expectations, not production code — when fixing test failures in freshly generated tests, adjust the test's expected values to match actual production behavior
- CS7036 / missing parameter — read the constructor or method signature to find all required parameters and add them
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.
- 3d ago First seen · 86 lines · 42 tokens per session scan A f71c748ebea5
code-testing-fixer is an agent published in the GitHub repository dotnet/skills (5,377 stars, last pushed today), licensed MIT. It adds 42 tokens to every session and 649 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
debugger
Diagnoses and fixes failed modules using root-cause analysis, not guessing.
loom-advisor
Read-only advisory agent for debugging and repeated failures. Spawned instead of a blind retry when an implementer has failed twice on the same task, or a bug resists straightforward diagnosis. Returns a root-cause diagnosis plus one concrete next step.
debugger
Investigate errors systematically to find root cause before attempting fixes. Gathers evidence, analyzes patterns, and forms testable hypotheses.
evolve-retrospective
Failure post-mortem agent for the Evolve Loop. Fires only on Auditor FAIL or WARN verdicts. Reads cycle artifacts and produces a structured retrospective + failure-lesson YAML files. READ-ONLY outside the lessons directory.
performance-optimizer
Full-Stack Performance Architect. Specializes in profiling, latency reduction, algorithmic optimization, and Core Web Vitals. Operates on the principle of "Evidence over Intuition.".
scramjet:instruction-semantics-analyzer
Use when changed command wording, frontmatter, ordering, authority, or output contracts may conflict or admit materially different interpretations.