dotnet▌

Enable nullable reference types in a C# project and systematically resolve all warnings. USE FOR: adopting NRTs in existing codebases, file-by-file or project-wide migration, fixing CS8602/CS8618/CS86xx warnings, annotating APIs for nullability, cleaning up null-forgiving operators, upgrading dependencies with new nullable annotations. DO NOT USE FOR: projects already fully migrated with zero warnings (unless auditing suppressions), fixing a handful of nullable warnings in code that already has NRTs enabled, suppressing warnings without fixing them, C# 7.3 or earlier projects. INVOKES: Get-NullableReadiness.ps1 scanner script.

Write new MSTest unit tests and implement concrete fixes in existing MSTest code using MSTest 3.x/4.x modern APIs and best practices. USE FOR: write unit tests for a class, write MSTest tests, create test class, fix test assertions, MSTest assertion APIs (StartsWith, EndsWith, MatchesRegex, IsGreaterThan, IsInRange, HasCount, IsNull), something seems off with my tests, review tests and fix issues, fix swapped Assert.AreEqual arguments, replace ExpectedException with Assert.Throws, modernize test patterns, convert DynamicData to ValueTuples, data-driven tests, test lifecycle setup, sealed test classes, async test patterns, cancellation token testing, test parallelization, Parallelize, DoNotParallelize, MSTest.Sdk project setup. DO NOT USE FOR: broad test quality audits or test smell detection (use test-anti-patterns), running tests (use run-tests), MSTest version migration (use migrate-mstest-v1v2-to-v3 or migrate-mstest-v3-to-v4).

Analyzes test suites and tags each test with a standardized set of traits (e.g., positive, negative, critical-path, boundary, smoke, regression). Use when the user wants to categorize, audit, or label tests with traits. Do not use for writing new tests, running tests, or migrating test frameworks.

Reference data for detecting the test platform (VSTest vs Microsoft.Testing.Platform) and test framework (MSTest, xUnit, NUnit, TUnit) from project files. DO NOT USE directly — loaded by run-tests, mtp-hot-reload, and migrate-vstest-to-mtp when they need detection logic.

Deep formal test smell audit based on academic research taxonomy (testsmells.org). Detects 19 categorized smell types — conditional logic, mystery guests, sensitive equality, eager tests, and more — with calibrated severity and research-backed remediation. Use for comprehensive test suite health assessments. For a quick pragmatic review, use test-anti-patterns instead. DO NOT USE FOR: writing new tests (use writing-mstest-tests), evaluating assertion quality specifically (use assertion-quality), or finding test duplication and boilerplate (use exp-test-maintainability).

Suggests using Microsoft Testing Platform (MTP) hot reload to iterate fixes on failing tests without rebuilding. Use when user says "hot reload tests", "iterate on test fix", "run tests without rebuilding", "speed up test loop", "fix test faster", or needs to set up MTP hot reload to rapidly iterate on test failures. Covers setup (NuGet package, environment variable, launchSettings.json) and the iterative workflow for fixing tests. DO NOT USE FOR: writing test code, diagnosing test failures, running tests normally with dotnet test (use run-tests), applying test filters, producing TRX reports, CI/CD pipeline configuration, or Visual Studio Test Explorer hot reload (which is a different feature).

Detection-focused review of .NET test code for anti-patterns that undermine reliability and diagnostic value. USE FOR: audit test quality, review test code, find test anti-patterns, tests pass but don't verify anything, flaky tests, ordering dependency, duplicate tests, magic values, missing/no assertions, swallowed exceptions, always-true assertions, over-mocking, test coupling, coverage touching, coverage inflation. DO NOT USE FOR: writing new tests (use writing-mstest-tests), direct MSTest API rewrites or implementation-only fixes such as swapped Assert.AreEqual argument order, running tests (use run-tests), migrating between frameworks (use migration skills), deep formal audit based on academic test smell taxonomy (use test-smell-detection).

Migrate a .NET 10 project or solution to .NET 11 and resolve all breaking changes. This is a MIGRATION skill — use it when upgrading from .NET 10 to .NET 11, NOT for writing new programs. USE FOR: upgrading TargetFramework from net10.0 to net11.0, fixing build errors after updating the .NET 11 SDK, resolving source-breaking and behavioral changes in .NET 11 runtime, C# 15 compiler, and EF Core 11, adapting to updated minimum hardware requirements (x86-64-v2, Arm64 LSE), and updating CI/CD pipelines and Dockerfiles for .NET 11. DO NOT USE FOR: .NET Framework migrations, upgrading from .NET 9 or earlier, greenfield .NET 11 projects, or cosmetic modernization unrelated to the upgrade. NOTE: .NET 11 is in preview. Covers breaking changes through Preview 3.

Performs pseudo-mutation analysis on .NET production code to find gaps in existing test suites. Use when the user asks to find weak tests, discover untested edge cases, check if tests would catch a bug, or evaluate test effectiveness through mutation-style reasoning. Analyzes production code for mutation points (boundary conditions, boolean flips, null returns, exception removal, arithmetic changes) and checks whether existing tests would detect each mutation. Works with MSTest, xUnit, NUnit, and TUnit. DO NOT USE FOR: writing new tests (use writing-mstest-tests), detecting test anti-patterns (use test-anti-patterns), measuring assertion diversity (use assertion-quality), or running actual mutation testing tools.

Migrates .NET test projects from xUnit.net v2 to xUnit.net v3. USE FOR: upgrading xunit to xunit.v3. DO NOT USE FOR: migrating between test frameworks (MSTest/NUnit to xUnit.net), migrating from VSTest to Microsoft.Testing.Platform (use migrate-vstest-to-mtp). For xUnit v3 MTP filter syntax (--filter-class, --filter-trait, --filter-query), also load migrate-vstest-to-mtp.