@types/chai

What is @types/chai?

The @types/chai package provides TypeScript type definitions for Chai, a BDD / TDD assertion library for node and the browser. This allows developers to use Chai in TypeScript projects with type checking and IntelliSense support in code editors.

What are @types/chai's main functionalities?

Expect/Should Assertions

Provides fluent API for asserting facts about values in a readable manner. Supports both 'expect' and 'should' styles.

expect(foo).to.be.a('string');
expect(foo).to.equal('bar');
expect(foo).to.have.lengthOf(3);
should.exist(foo);
foo.should.be.a('string');
foo.should.equal('bar');

Assert Style

Enables a more classical assert style, similar to node's assert module but with more capabilities.

assert.typeOf(foo, 'string');
assert.equal(foo, 'bar');
assert.lengthOf(foo, 3);

Property Assertions

Allows asserting the existence of an object's property, optionally asserting its value or properties.

expect(foo).to.have.property('length').with.lengthOf(3);
foo.should.have.property('length').with.lengthOf(3);

Other packages similar to @types/chai

@types/jest

Provides TypeScript definitions for Jest, a testing framework with a focus on simplicity. While Jest comes with its own assertion library, it's more tightly integrated with its testing environment compared to Chai, which is assertion library agnostic.

@types/mocha

Offers TypeScript definitions for Mocha, a feature-rich JavaScript test framework running on Node.js and in the browser. Mocha itself is more about the test framework rather than assertions, and it's often used in combination with Chai.

@types/sinon

Supplies TypeScript definitions for Sinon, a standalone test spies, stubs, and mocks for JavaScript. While not an assertion library, Sinon is commonly used alongside Chai for behavior verification in tests.

README

Installation

npm install --save @types/chai

Summary

This package contains type definitions for chai (http://chaijs.com/).

Details

Files were exported from https://github.com/DefinitelyTyped/DefinitelyTyped/tree/master/types/chai.

Additional Details

• Last updated: Mon, 05 May 2025 21:33:58 GMT
• Dependencies: @types/deep-eql

Credits

These definitions were written by Bart van der Schoor, Andrew Brown, Olivier Chevet, Matt Wistrand, Shaun Luttin, Satana Charuwichitratana, Erik Schierboom, Bogdan Paranytsia, CXuesong, and Joey Kilpatrick.