chai

library1.1.2jsnpmunverified

Chai is a widely used BDD/TDD assertion library for both Node.js and browser environments, designed to be framework-agnostic and pair delightedly with any JavaScript testing framework. The current stable version is 6.2.2, with frequent patch and minor releases, alongside periodic major updates, demonstrating an active development cadence.

testing

npm install chai

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INSTALL

IMPORT

SIG · CHAI

chai

testingjavascriptv1.1.2

Install

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Import

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Disk

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Pass rate

0/ 6

Env Coverage0 / 6

glibc

18–22

musl

18–22

Install & Compatibility

Where this runs

tested against v? · npm install

Install × environment matrix

Each cell = how many times install + import succeeded across repeated harness runs. Partial = flaky.
glibc = Debian/Ubuntu slim · musl = Alpine Linux

musl

node 18–226 runs

build_error

glibc

node 18–226 runs

build_error

Code

Verified usage

Verified import paths — ran on the pinned version, not inferred.

expect

✓ import { expect } from 'chai';

✗ const expect = require('chai').expect;

assert

✓ import { assert } from 'chai';

✗ const assert = require('chai').assert;

should

✓ import { should } from 'chai'; should();

✗ import { should } from 'chai';

This quickstart demonstrates basic assertions using Chai's Expect style, including numerical comparisons, boolean checks, and deep object equality.

import { expect } from 'chai'; const add = (a, b) => a + b; const isPositive = (num) => num > 0; // Basic assertions expect(add(2, 3)).to.equal(5); expect(add(-1, 5)).to.be.above(0); expect(isPositive(10)).to.be.true; // Deep equality for objects expect({ a: 1, b: 2 }).to.deep.equal({ a: 1, b: 2 });

Debug

Known issues

breakingChai v6.0.0 introduced a breaking change where direct imports from internal `lib/*.js` files are no longer supported. The library is now bundled into a single `index.js`.

fix

Update your imports to reference the main `chai` package directly, e.g., `import { expect } from 'chai';` instead of `import { expect } from 'chai/lib/expect';`.

affects: >=6.0.0

gotchaWhen using Chai's `should` assertion style, you must explicitly call `should()` after importing it to extend `Object.prototype` and enable the assertion syntax.

fix

After `import { should } from 'chai';`, add `should();` on the next line.

affects: >=1.0.0

gotchaImporting a Chai assertion style globally (e.g., `import 'chai/register-expect';`) modifies the global scope. While convenient for quick setups, this can lead to unexpected side effects or conflicts in larger projects.

fix

Prefer importing assertion styles locally (e.g., `import { expect } from 'chai';`) to avoid global pollution and ensure better test isolation.

affects: >=1.0.0

Errors

Common errors & fixes

Error [ERR_MODULE_NOT_FOUND]: Cannot find package 'chai/lib/expect' imported from ...

Attempting to import internal `lib/*.js` files directly after Chai v6.0.0, which bundled the library into a single `index.js`.

fix

Change the import path to `import { expect } from 'chai';` or `import { assert } from 'chai';`.

TypeError: (0 , chai__WEBPACK_IMPORTED_MODULE_0__.should) is not a function

Using Chai's `should` assertion style without calling `should()` after importing it, which is necessary to extend `Object.prototype`.

fix

Add `should();` immediately after the import statement: `import { should } from 'chai'; should();`.

ReferenceError: require is not defined

Attempting to use the CommonJS `require` function in an ECMAScript Module (ESM) file context (e.g., a `.mjs` file or a project with `"type": "module"` in `package.json`).

fix

Update your code to use ESM `import` statements, for example, `import { expect } from 'chai';` instead of `const expect = require('chai').expect;`.

Upgrade

Version history

1.1.2latest on npm

Audit

Dependencies

No dependency data recorded yet.

Agent activity

17 hits · last 30 days

node

OpenAI (training)

Resources

githubhttps://github.com/chaijs/chai ↗

packagehttps://www.npmjs.com/package/chai ↗

homepagehttps://www.chaijs.com ↗