write-xaml-tests

write-xaml-tests is a skill for Claude Code, Codex from dotnet/maui. It costs 49 tokens per session (742 once invoked), scanned A, original, MIT.

A testing guide for creating unit tests for XAML, Microsoft's markup language for describing user interfaces. It focuses on parsing, compilation, and source-generation behaviour rather than user interactions or visual rendering.

In plain words
What is it for?
Use it to test XAML parsing, XamlC compilation, generated source, bindings, markup extensions, names, and related XAML bugs.
Why use it?
It helps distinguish XAML-specific tests from tests that need to run a user interface, avoiding the wrong test type and conventions.

Skill for Claude CodeCodex

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 skills/dotnet/maui/write-xaml-tests
Any agent
npx skills add dotnet/maui --skill write-xaml-tests
Clone the repo
git clone --depth 1 https://github.com/dotnet/maui

Made for: Claude Code, Codex.

Wrote 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.

agentmods badge for write-xaml-tests

README.md
[![agentmods](https://agentmods.dev/badge/skills/dotnet/maui/write-xaml-tests.svg)](https://agentmods.dev/skills/dotnet/maui/write-xaml-tests)
Your own site
<a href="https://agentmods.dev/skills/dotnet/maui/write-xaml-tests"><img src="https://agentmods.dev/badge/skills/dotnet/maui/write-xaml-tests.svg" alt="Measured on agentmods" height="20"></a>
Per session 49 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.
When invoked 742 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 $0.00049 $0.00742
Opus 5 $0.00024 $0.00371
Sonnet 5 $0.00010 $0.00148
Haiku 4.5 $0.00005 $0.00074

Measured 4d ago against content hash d7ba42ad1533, method: parsed. Prices are Anthropic first-party input rates as of 2026-08-30, from the pricing page.

Security

Grade A, and why

write-xaml-tests 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 4d 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.

.github/skills/write-xaml-tests/SKILL.md · 92 lines

How it starts

The opening of the file, as written. The whole thing — 92 lines — stays where its author put it; the contents beside it link to each section on GitHub.

Write XAML Tests Skill

Creates XAML unit tests that verify XAML parsing, XamlC compilation, and source generation behavior.

When to Use

  • ✅ Testing XAML parsing/inflation behavior
  • ✅ Testing XamlC (IL generation) correctness
  • ✅ Testing Source Generator output
  • ✅ XAML-specific bugs (bindings, markup extensions, x:Name, etc.)

When NOT to Use

  • ❌ Testing UI interactions or visual behavior → Use write-ui-tests skill
  • ❌ Testing runtime behavior after page loads → Use write-ui-tests skill
  • ❌ Testing platform-specific rendering → Use write-ui-tests skill

Required Input

Before invoking, ensure you have:

  • Issue number (e.g., 12345)
  • Issue description - what XAML behavior is broken
  • Expected vs actual behavior

Workflow

Step 1: Read the XAML Unit Test Guidelines

cat .github/instructions/xaml-unittests.instructions.md

This contains the authoritative conventions for:

  • File naming (MauiXXXXX.xaml and MauiXXXXX.xaml.cs)
  • File location (src/Controls/tests/Xaml.UnitTests/Issues/)
  • Test patterns with [Values] XamlInflator
  • XamlC testing with MockCompiler
  • Source Generator testing with MockSourceGenerator
  • Special file extensions for invalid codegen (.rt.xaml, .rtsg.xaml, .rtxc.xaml)

Step 2: Create Test Files

Following the conventions from Step 1, create:

  • src/Controls/tests/Xaml.UnitTests/Issues/MauiXXXXX.xaml
  • src/Controls/tests/Xaml.UnitTests/Issues/MauiXXXXX.xaml.cs

Step 3: Verify Tests Compile and Run

# Build the test project
dotnet build src/Controls/tests/Xaml.UnitTests/Controls.Xaml.UnitTests.csproj -c Debug --no-restore -v q

# Run specific test
dotnet test src/Controls/tests/Xaml.UnitTests/Controls.Xaml.UnitTests.csproj --filter "FullyQualifiedName~MauiXXXXX" --no-build

Step 4: Verify Test Behavior

  • For bug reproduction tests: Tests should FAIL before fix, PASS after fix
  • For regression tests: Tests should PASS to confirm behavior works

Output

Read the full file on GitHub · 92 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. 4d ago First seen · 92 lines · 49 tokens per session scan A d7ba42ad1533

Subscribe to this mod's changes

write-xaml-tests is a skill published in the GitHub repository dotnet/maui (23,317 stars, last pushed 4d ago), licensed MIT. It adds 49 tokens to every session and 742 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 2026-08-30.

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