karma-esbuild-up

library3.0.0jsnpmunverified

karma-esbuild is a Karma preprocessor that compiles test files using esbuild, providing extremely fast transpilation and bundling for Karma test runners. Current stable version is 3.0.0, requiring Node >=16, esbuild >=0.17.0, and Karma >=6.0.0. It stands out for its speed and clean output, and supports single-bundle (all tests in one file) or per-file bundling. The package is actively maintained with regular releases on GitHub.

testing devops

npm install karma-esbuild-up

github ↗package ↗

INSTALL

IMPORT

SIG · KARMA-ESBUILD-UP

karma-esbuild-up

testingjavascriptv3.0.0

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.

default

✓ module.exports = function(config) { config.set({ preprocessors: { 'test/**/*.test.js': ['esbuild'] } }); }

✗ import karmaEsbuild from 'karma-esbuild'

Package is used as a Karma plugin via preprocessor name 'esbuild', not by importing directly. Configure it in karma.conf.js.

esbuild config

✓ config.set({ esbuild: { define: { 'process.env.NODE_ENV': '"production"' }, singleBundle: true } })

✗ config.set({ karmaEsbuild: { ... } })

Configuration is passed under the 'esbuild' key in Karma config, not 'karmaEsbuild'.

plugins

✓ config.set({ esbuild: { plugins: [myPlugin] } })

✗ config.set({ plugins: [myPlugin] })

Esbuild plugins are specified in the 'esbuild' config object, not the top-level 'plugins' array.

Basic Karma configuration with esbuild preprocessor, custom define, and single-bundle mode for Mocha tests.

// karma.conf.js module.exports = function (config) { config.set({ frameworks: ['mocha'], files: ['test/**/*.test.js'], preprocessors: { 'test/**/*.test.js': ['esbuild'], }, esbuild: { define: { 'process.env.VERSION': JSON.stringify(process.env.VERSION || 'development'), }, singleBundle: true, }, browsers: ['ChromeHeadless'], }); };

Debug

Known issues

breakingNode.js >=16 required, ESBuild >=0.17.0 peer dependency, Karma >=6.0.0 peer dependency

fix

Update Node, esbuild, and Karma to minimum versions. Check peer dependencies.

affects: >=3.0.0

gotchasingleBundle option defaults to true; if you have many test files, a single bundle may cause memory issues.

fix

Set `singleBundle: false` in esbuild config to generate a separate bundle per test file.

affects: >=2.2.0

deprecatedThe `args` option is removed; use `define` or `plugins` instead.

fix

Migrate custom arguments to esbuild `define` or pass them as plugins.

affects: >=2.1.3

gotchaConfiguration key must be `esbuild` (lowercase) in Karma config, not `karmaEsbuild`.

fix

Use `esbuild` key as shown in documentation.

affects: >=2.0.0

Errors

Common errors & fixes

Cannot find module 'karma-esbuild'

Package not installed or not in node_modules.

fix

Run `npm install --save-dev karma-esbuild`.

TypeError: Cannot read properties of undefined (reading 'define')

Missing or misconfigured esbuild config object.

fix

Ensure `esbuild` key is present in Karma config, e.g., `config.set({ esbuild: { define: {} } })`.

Error: esbuild plugin error: ...

Issue with a custom esbuild plugin passed to the esbuild config.

fix

Check the plugin implementation and ensure it's compatible with esbuild version.

Upgrade

Version history

3.0.0latest on npm

Audit

Dependencies

esbuildrequiredpeer dependency for compilation

karmarequiredpeer dependency for test runner integration

Agent activity

4 hits · last 30 days

node

Resources

githubhttps://github.com/marvinhagemeister/karma-esbuild ↗

packagehttps://www.npmjs.com/package/karma-esbuild-up ↗