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Is sinon-chai ESM-only? Can you require() it?

Extends Chai with assertions for the Sinon.JS mocking framework.

Last verified Sep 9, 2026 against sinon-chai@4.0.1. Markdown · JSON

ESM-only ESM-only since 4.0.0 — last CommonJS version is 3.7.0

sinon-chai dropped its CommonJS build in 4.0.0 (July 2024). The last version with a plain require()-able CommonJS entry is 3.7.0, published May 25, 2021.

On Node.js 20.19+, 22.12+ and newer, require("sinon-chai") works with the latest version: Node.js loads synchronous ES modules through require(). Verified on Node.js 20, 22, 24 and 26. On Node.js 18, which has no require(esm), require("sinon-chai") fails with ERR_REQUIRE_ESM.

What to do

  1. On Node.js 20.19+, 22.12+ and newer, require("sinon-chai") works with the latest version: Node.js loads synchronous ES modules through require(). Verified on Node.js 20, 22, 24 and 26.
  2. From a CommonJS file, use a dynamic import inside an async function: const sinonChai = await import("sinon-chai"). That works on every Node.js version the package supports.
  3. If you need a synchronous require() or run Node.js 18: npm install sinon-chai@3.7.0, the last CommonJS release (published May 25, 2021).
  4. TypeScript: npm install -D @types/sinon-chai
Latest
4.0.1 (Aug 22, 2025)
Module format
ESM-only
Last CommonJS version
3.7.0
ESM-only since
4.0.0 (Jul 25, 2024)
TypeScript types
@types/sinon-chai
Node engines
not declared
Weekly downloads
835K
License
(BSD-2-Clause OR WTFPL)

Does sinon-chai@4.0.1 actually load? Runtime test results

Installed and executed on Sep 9, 2026 with require("sinon-chai") from a CommonJS file and import "sinon-chai" from an ES module.

Runtimerequire("sinon-chai")import "sinon-chai"
Node.js 18✗ failsERR_REQUIRE_ESM✓ works
Node.js 20✓ works✓ works
Node.js 22✓ works✓ works
Node.js 24✓ works✓ works
Node.js 26✓ works✓ works
Bun 1.4.0✓ works✓ works

How to import sinon-chai

ES modules (import)

import * as sinonChai from "sinon-chai";

Namespace import shown because the ESM entry may have no default export; use named imports for what it exports.

CommonJS (require)

// Node.js 20.19+, 22.12+ and newer (verified):
const sinonChai = require("sinon-chai");

// Any Node.js version the package supports, from an async function:
async function main() {
  const sinonChai = await import("sinon-chai");
}

// Or pin the last CommonJS release:
// npm install sinon-chai@3.7.0

Module format by version

Derived from the type, main and exports fields of every stable release on npm, corrected where a runtime test of that version contradicted them (36 versions; the newest 36 shown).

VersionsFormatFirst published
4.0.0 – 4.0.1ESM-onlyJul 25, 2024
1.0.0 – 3.7.0CommonJSFeb 13, 2012

Frequently asked

Is sinon-chai ESM-only?

sinon-chai@4.0.1 is ESM-only. sinon-chai dropped its CommonJS build in 4.0.0 (July 2024). The last version with a plain require()-able CommonJS entry is 3.7.0, published May 25, 2021.

Which version of sinon-chai still supports CommonJS / require()?

3.7.0 is the last version of sinon-chai with a CommonJS build. Install it with "npm install sinon-chai@3.7.0". Every version from 4.0.0 on is ESM-only.

How do I use sinon-chai from a CommonJS file?

From a CommonJS file, use a dynamic import inside an async function: const sinonChai = await import("sinon-chai"). That works on every Node.js version the package supports. On Node.js 20.19+, 22.12+ and newer, require("sinon-chai") works with the latest version: Node.js loads synchronous ES modules through require(). Verified on Node.js 20, 22, 24 and 26. Alternatively pin sinon-chai@3.7.0.

Does sinon-chai work in Bun?

Yes. import "sinon-chai" loaded successfully in Bun 1.4.0 on Sep 9, 2026.

Does sinon-chai ship TypeScript types?

Not bundled. Install the community types with "npm install -D @types/sinon-chai".

Links

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