testing

Runtime and type tests serve different purposes in TypeScript projects. Runtime tests use Vitest to verify behavior; type tests use utilities like Expect and AssertEqual to verify type correctness. This Skill teaches when to apply each approach and how to structure both alongside your code for comprehensive coverage.

TDD is a development cycle where you write tests before implementation. This Skill details a 5-step TDD process: capture initial state (Snapshot), log observations, write tests, implement the feature, and close out. Following this workflow ensures your code meets requirements and maintains type safety.

Effective test organization requires clear structure and consistent conventions. This Skill provides guidance on arranging runtime tests with Vitest and type tests with type-test utilities, including test naming, assertion patterns (Expect, AssertTrue, AssertFalse, AssertExtends), and linting conventions for maintainable, deterministic tests.

Type tests often fail due to incorrect assertion syntax or misunderstanding type inference. This Skill highlights frequent errors in type testing and explains best practices for writing reliable type assertions, helping you avoid pitfalls and ensure your types behave as expected.

Vitest handles runtime tests directly, but type testing requires separate utilities like inferred-types or type-test. This Skill explains how to integrate Vitest for runtime tests (pnpm test) and type-test utilities for type validation (pnpm test:types) in a unified testing strategy.

Comprehensive testing covering both runtime behavior and type correctness ensures software reliability. This Skill teaches how to write effective tests, adopt TDD practices, and integrate testing tools to maintain high code quality and catch errors before production.