@deessejs/type-testing

A micro library for compile-time type testing in TypeScript.

Requirements

• TypeScript 5.0+

Installation

# Install type-testing
npm install @deessejs/type-testing

# Or using pnpm
pnpm add @deessejs/type-testing

# Or using yarn
yarn add @deessejs/type-testing

Usage

import { Equal, check, assert, expect } from '@deessejs/type-testing'

// Simple type equality
type Test = Equal<string, string>  // true

// Chainable API
check<string>().equals<string>()   // passes

// Assert with clear errors
assert<{ a: string }>().hasProperty('a')

// Expect syntax
expect<string, string>().toBeEqual()

Features

• Type Equality - Strict and simple equality checks
• Special Type Detection - IsAny, IsNever, IsUnknown, IsVoid, etc.
• Union/Tuple/Array Detection - IsUnion, IsTuple, IsArray
• Type Inhabitation - IsInhabited, IsUninhabited
• Property Testing - HasProperty, PropertyType
• Property Modifiers - IsReadonly, IsRequired, IsPublic, IsPrivate, IsProtected
• Deep Type Manipulation - DeepReadonly, DeepPartial, RequiredKeys, OptionalKeys
• Function Types - Parameters, ReturnType, Parameter
• Constructor/Abstract - IsConstructor, IsAbstract
• Special Equality - IsNeverEqual
• Chainable API - check(), assert(), expect() for fluent testing

API Reference

Types

Type	Description
Equal<T, U>	Strict equality check
NotEqual<T, U>	Inequality check
IsNeverEqual<T, U>	Check if both types are never
IsAny<T>	Check if type is any
IsNever<T>	Check if type is never
IsUnknown<T>	Check if type is unknown
IsNullable<T>	Check if type is null | undefined
IsUnion<T>	Check if type is a union
IsTuple<T>	Check if type is a tuple
IsArray<T>	Check if type is an array
IsReadonly<T>	Check if all properties are readonly
IsRequired<T>	Check if all properties are required
IsPublic<T, K>	Check if property is public
IsPrivate<T, K>	Check if property is private
IsProtected<T, K>	Check if property is protected
DeepReadonly<T>	Make all properties readonly recursively
DeepPartial<T>	Make all properties optional recursively
RequiredKeys<T>	Get keys of required properties
OptionalKeys<T>	Get keys of optional properties
IsConstructor<T>	Check if type is a constructor
IsAbstract<T>	Check if type is abstract

Functions

Function	Description
check<T>()	Create a chainable type checker
assert<T>()	Create an assert type checker (throws on failure)
expect<T, U>()	Create an expect-style type checker

For complete documentation, see packages/type-testing/README.md

Contributing

Contributions are welcome! Please feel free to submit a Pull Request.

Author

• Nesalia Inc.

Security

If you discover any security vulnerabilities, please send an e-mail to security@nesalia.com.

License

MIT License - see the LICENSE file for details.