microsoft/testfx.

assertion-quality

Analyze assertion quality, depth, variety, and false confidence in existing tests. ALWAYS USE when asked about weak, shallow, trivial, always-true, self-referential, assertion-free, presence/truthiness-only, or insufficiently diverse assertions, including MSTest, Jest, pytest, and Go. DO NOT USE for direct fixes: writing-mstest-tests owns supplied MSTest assertions; code-testing owns new cases. Use test-gap-analysis when asked whether tests would catch a production change, and test-anti-patterns for general severity-ranked audits.

behavior-preserving-refactor

Preserve observable behavior when splitting files, moving members, consolidating helpers, or simplifying TestFx code. Use for structural refactors and file-diet implementation; inventory baseline semantics and consumers, then run focused equivalence checks.

binlog-failure-analysis

Diagnose existing MSBuild .binlog failures with MCP/replay; not log capture or non-MSBuild failures.

binlog-generation

Capture and verify unique MSBuild binlogs, quoting '-bl:{}' in PowerShell; not analysis of existing logs.

build-parallelism

Analyze an MSBuild solution, solution filter, or Build.proj that schedules multiple project files. USE FOR: measured idle worker nodes, `-m` that does not scale, a serial ProjectReference critical path, graph builds, or an MSBuild task that builds a Projects list. Requires at least two distinct project files whose scheduling or throughput must be analyzed. DO NOT USE for non-MSBuild build systems.

build-perf-baseline

Measure repeatable cold/changed-input/no-op MSBuild baselines for caching, output layout and graph tuning; not task diagnosis or non-MSBuild builds.

build-perf-diagnostics

Diagnose MSBuild target/task/analyzer bottlenecks from binlogs after baselining; not baseline setup, incremental correctness or parallelism tuning.

check-bin-obj-clash

Detects MSBuild projects with conflicting OutputPath or IntermediateOutputPath. USE FOR: builds failing with 'Cannot create a file when that file already exists', 'The process cannot access the file because it is being used by another process', intermittent build failures that succeed on retry, or missing/overwritten outputs in multi-project or multi-targeting builds where bin/obj (or project.assets.json) collide. Common causes: shared OutputPath, missing AppendTargetFrameworkToOutputPath, extra global properties (e.g. PublishReadyToRun), or SetTargetFramework on a ProjectReference to a single-targeting project. DO NOT USE FOR: file access errors unrelated to MSBuild (OS-level locking), single-project single-TFM builds, non-MSBuild build systems.

code-testing

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code-testing-agent

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code-testing-extensions

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copy-to-output-directory

For legacy copy-mode links or direct calls, invoke msbuild for CopyToOutputDirectory guidance.

coverage-analysis

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crap-score

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csharp-expert

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csharp-refactoring

Safely refactors C#/.NET code without changing behavior. USE FOR any request to refactor, rename, move, extract, inline, merge, consolidate, deduplicate, split, or modernize C# code, including partial/generated declarations, wrappers, public APIs, serialization/reflection/configuration names, friend assemblies, conditional compilation, and multi-targeted projects. Also use when a request calls a feature, bug fix, package/framework upgrade, or public nullability change a refactor and the behavior-changing part must be separated or declined. DO NOT USE FOR ordinary feature or bug fixes not presented as refactoring; standalone upgrades after reclassification (use dotnet-upgrade); adding tests; or formatting-only work.

curation-exceptions

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detect-static-dependencies

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directory-build-organization

USE ONLY for (1) two or more projects with repeated MSBuild policy, targets, or package versions, or (2) an existing Directory.Build.props/targets/rsp hierarchy with an import, placement, or layering defect. A one-project repo without an existing Directory.Build file is outside scope; do not load this skill. Covers centralizing shared policy and targets, Directory.Packages.props across projects, parent hierarchy/import structure, props-versus-targets placement, and folder/project exceptions. An existing hierarchy defect remains in scope when only one project is affected. For property value or condition semantics use property-patterns. Exclude legacy-to-SDK migration and non-MSBuild systems.

eliminate-redundant-restores

Remove repeated NuGet restores from multi-step .NET builds safely. USE FOR: build/test/publish steps that each restore, Directory.Build.rsp with -restore, safe restore suppression, NETSDK1004/NETSDK1047 after --no-restore. DO NOT USE FOR: slow first restore, only one restore, version or lock errors, unranked build slowness (use build-perf-baseline).

eval-performance

Diagnose measured MSBuild evaluation costs in globs, imports and properties; not compilation, target-execution or incremental-build problems.

extension-points

Trace MSBuild hook/import discovery and NuGet packed assets; not a single Import/Exists safety verdict, props/targets placement or target incrementality.

feature-delivery

Keep TestFx feature research and decision records, challenge material design choices, plan consumer E2E coverage, inspect rendered UI/layout, and prove regression-test sensitivity. Use before new features or material design decisions, when adding regression coverage, and when preparing feature PR evidence.

filter-syntax

Reference-only filter syntax for VSTest and MTP with MSTest, NUnit, xUnit v3, and TUnit. Load only after the platform/framework is known and a consumer needs to create or translate a filter. Do not load for unfiltered runs or platform detection. Used by run-tests and mtp-hot-reload; never invoke directly.

find-untested-sources

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generate-testability-wrappers

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grade-tests

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including-generated-files

Own MSBuild generated-artifact integration. USE FOR: a target that creates or should create source, Content, None, or another physical file but the artifact is missing from compilation or output; target timing; evaluation-time glob misses; $(IntermediateOutputPath) placement; and FileWrites clean tracking. The prompt may describe the generated artifact without naming the producing task. DO NOT USE when the primary defect is general Include/Remove/Update semantics, item metadata or batching, duplicate/overlapping declarations, or a generated-item identity relationship; use item-management. Exclude Roslyn source-generator internals and non-MSBuild systems.

incremental-build

Diagnose unnecessary MSBuild target execution via inputs/outputs and no-change builds; not first-build cost, parallelism or evaluation slowness.

item-management

Own concrete MSBuild ItemGroup and item-expression questions. USE FOR: Include, Remove, Update, item identity and metadata, transforms, filtering, batching, duplicate or overlapping items, and reviews that verify whether those operations are correct. Generated items stay in scope when the central defect is item identity, metadata, batching, duplicate declarations, or glob/Remove/Update semantics. For a generated artifact missing from compilation or output, wrong target timing/path, or FileWrites clean tracking without a broader item-semantics defect, use including-generated-files. The item operation may be broken, suspected, or already correct. Exclude property-only issues, general incrementality with no item question, broad reviews with no concrete item concern, and non-MSBuild systems.

migrate-static-to-wrapper

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msbuild

Use only for MSBuild failure investigation, build-performance analysis, or review of existing build XML/extension contracts. A plan to convert a working legacy/non-SDK project to SDK style or migrate packages.config is a project-system migration, NOT a build-file review: do not activate, even to check scope. Framework/API upgrades are also excluded. Activate for advisory Import/Exists hook and NuGet packed-import questions even without a checkout or failed build; .csproj/.fsproj/.vbproj/.props/.targets conditions; custom-target inputs/outputs; .binlog capture/replay; failing dotnet build/restore/pack/publish or MSBuild-based test builds; slow evaluation, compilation, copying, or no-change builds; and controlled timing comparisons. Exclude SDK installation alone, C# refactoring, runtime profiling, assertions after successful builds, and non-MSBuild builds.

msbuild-antipatterns

Review/audit MSBuild XML correctness and maintainability, including F# order and Import safety; not SDK-style migration. Do not edit unless fixes are requested.

msbuild-modernization

Guide for modernizing and migrating MSBuild project files to SDK-style format. USE FOR: converting legacy .csproj/.vbproj with verbose XML to SDK-style, migrating packages.config to PackageReference, removing Properties/AssemblyInfo.cs in favor of auto-generation, eliminating explicit Compile Include lists via implicit globbing, consolidating shared settings into Directory.Build.props. Indicators of legacy projects: ToolsVersion attribute, an Import of Microsoft.CSharp.targets via $(MSBuildToolsPath), .csproj files over 50 lines for simple projects. DO NOT USE FOR: projects already in SDK-style format, non-.NET build systems (npm, Maven, CMake), .NET Framework projects that cannot move to SDK-style.

msbuild-server

Guide for using MSBuild Server to improve CLI build performance. Activate when developers report slow incremental builds from the command line, or when CLI builds are noticeably slower than IDE builds. Covers MSBUILDUSESERVER=1 environment variable for persistent server-based caching. Do not activate for IDE-based builds (Visual Studio already uses a long-lived process).

mtp-hot-reload

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platform-detection

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post-release-activities

Systematic activities that need to be performed after a release is done.

property-patterns

Diagnose and fix concrete MSBuild property defects in projects and existing shared-file hierarchies. USE FOR: conditions, defaults, append versus overwrite, last-write-wins values, OS/TFM checks, portable paths, normalization, and reviews centered on those property defects. Property defects in Directory.Build.* remain in scope, including overwritten values across parent/child imports and conditions that run before TargetFramework is set, even when the fix changes import order or moves a property group to .targets. DO NOT USE FOR: placement-only or import-only requests with no concrete property defect, such as discovering shared files or choosing which file owns a target or customization (use directory-build-organization); item operations; target structure; broad reviews without a concrete property defect; non-MSBuild work.

resolve-project-references

Guide for interpreting ResolveProjectReferences time in MSBuild performance summaries. Activate when ResolveProjectReferences appears as the most expensive target and developers are trying to optimize it directly. Explains that the reported time includes wait time for dependent project builds and is misleading. Guides users to focus on task self-time instead. Do not activate for general build performance -- use build-perf-diagnostics instead.

run-tests

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scaffold-dotnet-test-project

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session-delivery-hygiene

Gate local-session scope, persistent delivery, live PR state, integration provenance, and owned cleanup. Use before implementing guidance changes, changing or pushing PR work, diagnosing package/output mismatches, or handing off implementation.

setup-local-sdk

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target-authoring

Canonical patterns for writing custom MSBuild targets. USE FOR: diagnosing and fixing custom target authoring anti-patterns; broken SDK target chains across files (e.g., Directory.Build.targets silently redefining SDK targets); targets that replace CompileDependsOn instead of extending it with $(CompileDependsOn); query targets returning stale results from Outputs vs Returns misuse; missing Inputs/Outputs causing unnecessary rebuilds; missing FileWrites registration. Covers DependsOnTargets vs BeforeTargets vs AfterTargets, the Build→CoreBuild three-level pattern, and the $(XxxDependsOn) chain-extension pattern. DO NOT USE FOR: incremental build tuning (use incremental-build), parallelization (use build-parallelism), general anti-patterns (use msbuild-antipatterns), non-MSBuild build systems.

test-analysis-extensions

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test-anti-patterns

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test-gap-analysis

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test-smell-detection

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test-tagging

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test-value-evidence

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testability-obstacle

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testfx-acceptance-validation

Validate TestFx shipping paths and capable CI execution using packed consumers, package/cache provenance, exact exits and artifacts, and selected-versus-executed test evidence. Use for acceptance regressions, package/MSBuild/launcher/protocol changes, or skipped-only CI results; not for unrelated unit-only or documentation changes.

testfx-localization-validation

Validate generated TestFx localization catalogs, resource IDs, placeholders and locked tokens. Use for RESX/XLF changes, OneLoc PRs, localization build failures, duplicate targets or units, and orphaned translation entries.

testfx-parallel-safety-preflight

Check concurrency and isolation before implementing or refactoring TestFx tests, lifecycle code, helpers, shared-state declarations, or production paths those tests exercise. Use before narrowing DoNotParallelize or ResourceLock, changing parallelization settings, or introducing asynchronous workers; repeat against the final diff.

testfx-test-value-evidence

Apply the vendored test-value-evidence skill with TestFx toolchain, assertion, parallel-safety, packed-consumer, and review conventions. Use when implementing or reviewing behavior-changing TestFx PRs or commits, including source-only changes.

troubleshoot-binlog-mcp

Diagnose dotnet-msbuild binlog MCP startup failures. USE FOR: CONNECTION_CLOSED, binlog server won't connect, missing binlog tools, Microsoft.AITools.BinlogMcp not found, dnx launch errors. Checks workspace SDK, feeds, and source mapping without bypassing policy. DO NOT USE FOR: errors inside a binlog (use binlog-failure-analysis), capturing binlogs (use binlog-generation), unrelated MCP servers.

writing-mstest-tests

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