When to Apply: Reference when writing .NET unit tests with xUnit, using [Theory] with InlineData for parameterized tests, or integration testing ASP.NET Core apps with WebApplicationFactory. Triggers on "xUnit", "[Fact]", "[Theory]", "Assert.Equal", "C# xUnit".
Playbook Deep Dive (10 sections): §1 Project Setup & Configuration · §2 Test Patterns — Fact & Theory · §3 Shared Context — IClassFixture & ICollectionFixture · §4 Async Testing & Custom Assertions · §5 Test Data Generation with Bogus · §6 Integration Testing with WebApplicationFactory · §7 Logging & Output · §8 CI/CD Integration · §9 Debugging Table · §10 Best Practices
The agent loads from 2 on-demand reference files (advanced-patterns.md, playbook.md) containing detailed implementation guides, cloud integration patterns, debugging tables, and language-specific best practices.