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test-your-types

Validate TypeScript type declarations with structured type-level tests.

Updated Jul 17, 2017
Search Tags:#typescript#vitest#types#type-testing#expect-type#tsd#type-utils
One-click install
npx skills add https://github.com/luyi985/lyi-bash --skill test-your-types
Or copy as Structured Prompt for Agent▼
Please help me install this Agent Skill.
Skill: test-your-types
Source: https://github.com/luyi985/lyi-bash/tree/main/ai/skills/test-your-types
Command: npx skills add https://github.com/luyi985/lyi-bash --skill test-your-types

SYSTEM DOCUMENTATION & REQUIREMENTS

What problem does it solve?

Type-level code can have bugs too, and type declarations can drift out of sync with implementations. Testing types ensures correctness, catches drift, and improves maintainability across libraries and complex utilities.

Core Features & Use Cases

  • Write type tests for libraries, complex type utilities, and when types and implementations are in separate files.
  • Validate that valid types compile and invalid types error with helpful messages.
  • Use examples and patterns across TypeScript projects to verify type behavior during refactoring or library evolution.

Quick Start

Create and run a small type-level test to verify that a nested type becomes deeply readonly.

Frequently Asked Questions about test-your-types

High-intent search queries and answers about installing and using this skill.

FAQPage Schema
How do I test TypeScript types to ensure they match the implementation?▼

You can test TypeScript types by writing structured type-level tests that verify valid types compile and invalid types error correctly, catching drift between declarations and implementations in libraries.

What is type testing and when do I need it in my TypeScript project?▼

Type testing is the practice of validating type declarations through structured tests. You need it when type logic is complex, types and implementations are in separate files, or when refactoring library utilities to ensure maintainability.

How do I validate that invalid TypeScript types throw helpful error messages?▼

Validate invalid TypeScript types by applying type-level testing tools to assert that incorrect type usages produce expected compiler errors and helpful messages, ensuring type safety and clear developer feedback.

Can I use Vitest to test complex TypeScript type utilities?▼

Yes, Vitest can be used alongside tools like expect-type and tsd to run type-level tests for complex TypeScript type utilities, verifying that type behavior remains correct during refactoring or library evolution.

What is the best way to prevent type declaration drift in TypeScript libraries?▼

The best way to prevent type declaration drift is to implement type-level tests that continuously validate both valid type compilation and expected errors, ensuring type declarations and implementations stay synchronized.

Does expect-type work for testing TypeScript types in separate implementation files?▼

Yes, expect-type is suitable for testing TypeScript types when declarations and implementations are in separate files, allowing you to write structured tests that verify type correctness and expected error behavior.

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