Dotnet Testing

.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