What problem does it solve? Writing C# unit tests with outdated MSTest patterns leads to unclear failure messages, obsolete APIs like [ExpectedException], and missed opportunities for type-safe data-driven testing. This Skill provides current MSTest 3.x/4.x best practices so tests are maintainable and expressive. ## Core Features & Use Cases - Modern Assertion APIs: Covers Assert.Throws, Assert.ThrowsExactly, collection assertions, comparison assertions, and the MSTest 4.0 Assert.That API with correct argument ordering. - Data-Driven Tests: Guides DataRow and DynamicData usage, preferring type-safe ValueTuple and TestDataRow sources over IEnumerable<object[]>. - Lifecycle and TestContext: Documents execution order, constructor-based setup, TestContext injection, cancellation tokens, retries, conditional execution, and parallelization. - Use Case: When adding tests to a C# service class, apply the AAA pattern, seal test classes, use Assert.ThrowsExactly for exception checks, and parameterize edge cases with DynamicData ValueTuple sources. ## Quick Start Write MSTest unit tests for my Calculator class using modern assertion APIs and data-driven test cases.
