esmocha

library5.0.0jsnpmunverified

Mocha wrapper with built-in TypeScript support via esbuild, integrated Jest-compatible expect, mock, and snapshot testing. Current stable version is v5.0.0, released in 2025. Release cadence is irregular with major versions marking breaking changes. Key differentiators include zero-config TypeScript execution, Jest-compatible API for familiar testing patterns, and automatic ESM support for Node >=18.

testing

npm install esmocha

github ↗package ↗

INSTALL

IMPORT

SIG · ESMOCHA

esmocha

testingjavascriptv5.0.0

harness data pending

Install & Compatibility

Where this runs

No compatibility data collected yet for this library.

Code

Verified usage

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

expect

✓ import { expect } from 'esmocha'

ESM-only since v1; no CommonJS support.

mock

✓ import { mock } from 'esmocha'

resetAllMocks

✓ import { resetAllMocks } from 'esmocha'

afterAll

✓ import { afterAll } from 'esmocha'

✗ import { afterAll } from 'mocha'

Re-exported from mocha; prefer importing from esmocha for consistency.

Installs esmocha, creates a simple TypeScript module and test, then runs the test using esmocha.

npm install esmocha --save-dev echo "export function add(a: number, b: number) { return a + b; }" > add.ts echo "import { expect } from 'esmocha'; import { add } from './add.js'; describe('add', () => { it('should add two numbers', () => { expect(add(1, 2)).toBe(3); }); });" > test.spec.ts npx esmocha

esmocha --version

Debug

Known issues

breakingv5.0.0 makes loader optional; if you relied on automatic esbuild loader, you may need to register it manually.

fix

Use --loader @node-loaders/esbuild or configure in mocha options.

affects: >=5.0.0

breakingv4.0.0 updated mocha-expect-snapshot and jest-mock, potentially breaking snapshot file formats.

fix

Update snapshots with npx esmocha --update-snapshot.

affects: >=4.0.0

gotchaesmocha is ESM-only; require() will fail.

fix

Use import syntax and ensure package.json has type: module.

affects: >=1.0.0

gotchaNode.js version must be ^18.19.0 || ^20.9.0 || ^22.0.0 || >=24.0.0; older versions may not work.

fix

Upgrade Node to supported version.

affects: >=5.0.0

Errors

Common errors & fixes

Error [ERR_REQUIRE_ESM]: require() of ES Module esmocha not supported.

Attempted to use require with ESM-only package.

fix

Change to import { expect } from 'esmocha' and enable ESM in your project.

TypeError: Expect is not a function

Misconfigured import: using default import instead of named import.

fix

Use import { expect } from 'esmocha' rather than import expect from 'esmocha'.

Error: Cannot find module '@node-loaders/esbuild'

Missing peer dependency @node-loaders/esbuild.

fix

Run npm install @node-loaders/esbuild --save-dev.

Upgrade

Version history

5.0.0latest on npm

Audit

Dependencies

@node-loaders/esbuildrequiredprovides TypeScript transformation

mocharequiredtest runner wrapper

Agent activity

4 hits · last 30 days

node

Resources

githubhttps://github.com/mshima/esmocha ↗

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