Detects MSBuild projects with conflicting OutputPath or IntermediateOutputPath. Only activate in MSBuild/.NET build context. 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, missing outputs in multi-project builds, multi-targeting builds where project.assets.json conflicts. Diagnoses when multiple projects or TFMs write to the same bin/obj directories due to shared OutputPath, missing AppendTargetFrameworkToOutputPath, or extra global properties like PublishReadyToRun creating redundant evaluations. DO NOT USE FOR: file access errors unrelated to MSBuild (OS-level locking), single-project single-TFM builds, non-MSBuild build systems. INVOKES: binlog MCP server tools (overview, projects, evaluations, properties, double_writes); falls back to dotnet msbuild binlog replay + grep when the MCP is unavailable.
Generates and writes new unit tests for any programming language — scaffolds .NET test projects, pytest suites, Vitest/Jest suites, Go test files, and JUnit suites, and configures coverage tooling (coverlet, pytest-cov, @vitest/coverage-v8) as part of test generation. Use when asked to generate tests, generate pytest tests, generate Vitest tests, write unit tests, add tests, improve coverage, comprehensive tests, or scaffold a new test project or suite for an app, service, library, REST API, blueprint, or package — including project-wide, multi-file test generation across services, repositories, routes, and modules. Supports C#/.NET, Python (pytest, Flask/Django), TypeScript/JavaScript (Vitest, Jest, Mocha), Go, Rust, Java (JUnit). Runs a research, planning, and implementation pipeline so tests compile and pass. DO NOT USE FOR: running existing tests (use run-tests); analyzing existing coverage reports (use coverage-analysis or crap-score); MSTest modernization (use writing-mstest-tests).
Provides file paths to language-specific extension files for the code-testing pipeline. Call this skill to discover available extension guidance files (e.g., dotnet.md for .NET, cpp.md for C++). Do not use directly — invoked by code-testing agents and skills that need language-specific references.
Guide for MSBuild extensibility: CustomBefore/CustomAfter hooks, wildcard imports with alphabetic ordering, import gating with control properties, NuGet package build extension layout (build/buildTransitive), and the MicrosoftCommonPropsHasBeenImported guard. Only activate in MSBuild/.NET build context. USE FOR: diagnosing and fixing MSBuild import and hook patterns, reviewing and fixing extension point anti-patterns in Directory.Build files, fixing missing Exists() guards on imports that break fresh clones, fixing NuGet package hooks being silently dropped instead of appended, making build targets extensible for other projects, injecting custom logic into the build pipeline, creating NuGet packages that extend the build, conditionally disabling imports. DO NOT USE FOR: target authoring patterns (use target-authoring), props vs targets placement (use directory-build-organization), general anti-patterns (use msbuild-antipatterns), non-MSBuild build systems.
Polyglot, parse-only static analysis that pairs source files with referencing tests across Python, TypeScript/JavaScript, Go, Java, Rust, C#, and Ruby. JSON shape matches `find-untested-sources`. USE FOR: where to write tests next, find untested files, list sources without tests, polyglot test-pairing map. DO NOT USE FOR: coverage, CRAP risk. For .NET-only repos prefer `find-untested-sources`.
Parse-only C# analysis that pairs source files with referencing tests and emits JSON: `source_to_tests`, `untested` ordered by declaration count, and `suggested_test_path` from `ProjectReference` edges. USE FOR: where to write tests next, find untested files, list sources without tests, build a test-pairing map. DO NOT USE FOR: coverage (use `coverage-analysis`), CRAP risk ranking, assertion gaps.
Catalog of MSBuild anti-patterns with detection rules and fix recipes. Only activate in MSBuild/.NET build context. USE FOR: reviewing, auditing, or cleaning up .csproj, .vbproj, .fsproj, .props, .targets, or .proj files. Each anti-pattern has a symptom, explanation, and concrete BAD→GOOD transformation. Covers Exec-instead-of-built-in-task, unquoted conditions, hardcoded paths, restating SDK defaults, scattered package versions, and more. DO NOT USE FOR: non-MSBuild build systems (npm, Maven, CMake, etc.), project migration to SDK-style (use msbuild-modernization).
Scans .NET code for ~50 performance anti-patterns across async, memory, strings, collections, LINQ, regex, serialization, and I/O with tiered severity classification. Use when analyzing .NET code for optimization opportunities, reviewing hot paths, or auditing allocation-heavy patterns.