dotnet-testing

name	dotnet-testing
description	Write and run .NET tests following TDD principles. Use when writing tests, implementing TDD workflow, verifying test coverage, or debugging test failures.

.NET Testing Standards

When to Use This Skill

Use this skill when you need to:

• Write unit tests for new functionality
• Follow TDD (Test-Driven Development) workflow
• Debug failing tests
• Review test quality and coverage

Prerequisites

Before writing tests: Read .planning/CONVENTIONS.md for repository-specific test patterns (framework, naming, mocking library). If it doesn't exist, the calling agent should invoke the Repo Analyser subagent first.

Hard Rules

Must

1. Write failing test first (TDD) — Test drives the implementation, not vice versa
2. One assertion concept per test — Test one behaviour, multiple asserts on same object is OK
3. Use repo's existing test framework — Don't mix xUnit and NUnit in same solution
4. Tests must be deterministic — No dependency on time, random, or external state
5. Follow repo's naming convention — Check CONVENTIONS.md for pattern
6. Test behaviour, not implementation — Tests should survive refactoring

Must Not

1. Test private methods directly — Test through public API; if you need to test private, extract a class
2. Use Thread.Sleep in tests — Use async/await, polling with timeout, or test doubles
3. Share mutable state between tests — Each test gets fresh state
4. Mock what you don't own — Wrap third-party APIs, mock the wrapper
5. Write tests for trivial code — Auto-properties, simple DTOs don't need tests
6. Depend on test execution order — Tests must run independently and in parallel

TDD Workflow

1. RED — Write a test that expects the behaviour. Run it — it MUST fail. If it passes, the test is wrong or the feature already exists.
2. GREEN — Write the MINIMUM code to make the test pass. Hard-coding is acceptable if it satisfies the test.
3. REFACTOR — Remove duplication, improve naming, extract methods/classes. Run ALL tests — they MUST still pass.

Commands Reference

All dotnet commands work identically across all shells.

dotnet test
dotnet test ./tests/MyProject.UnitTests/
dotnet test --filter "FullyQualifiedName~OrderServiceTests"
dotnet test --filter "Category=Unit"
dotnet test --filter "FullyQualifiedName!~IntegrationTests & FullyQualifiedName!~Integration.Tests"
dotnet test --list-tests
dotnet test --collect:"XPlat Code Coverage"

The compound filter excludes all tests from integration test projects — covering both IntegrationTests and Integration.Tests naming conventions. Use this when integration tests are excluded via the quality-gates skill protocol.

Verification Checklist

Before considering tests complete:

• Test fails before implementation (TDD RED)
• Test passes after implementation (TDD GREEN)
• Refactoring done with tests still passing
• Follows naming convention from CONVENTIONS.md
• One behaviour per test
• No flaky/non-deterministic elements
• Mocks are for external dependencies only
• Test class has same structure as others in repo