Code coverage using Istanbul for Ember apps and addons. Supports classic Ember CLI, Embroider, and Vite-based builds.

• Node.js >= 20

The following apply to classic ember-cli / Embroider builds only (not Vite):

• ember-cli-babel >= 6.0.0
• If using Mocha, Testem >= 1.6.0 for which you need ember-cli > 2.4.3
• If using Mirage you need ember-cli-mirage >= 0.1.13
• If using Pretender (even as a dependency of Mirage) you need pretender >= 0.11.0
• If using Mirage or Pretender, you need to set up a passthrough for coverage to be written.

• ember install ember-cli-code-coverage

Or with npm/pnpm:

npm install --save-dev ember-cli-code-coverage
# or
pnpm add -D ember-cli-code-coverage

In order to gather code coverage information, you must first install the Babel plugins in each project that you'd like to have instrumented.

For classic apps (ember-cli-build.js):

let app = new EmberApp(defaults, {
  babel: {
    plugins: [...require('ember-cli-code-coverage').buildBabelPlugin()],
  },
});

For embroider apps (ember-cli-build.js):

let app = new EmberApp(defaults, {
  babel: {
    plugins: [...require('ember-cli-code-coverage').buildBabelPlugin({ embroider: true })],
  },
});

For in-repo and standalone addons (index.js):

module.exports = {
  name: require('./package').name,

  options: {
    babel: {
      plugins: [...require('ember-cli-code-coverage').buildBabelPlugin()],
    },
  },
};

For in-repo engines (index.js):

module.exports = EngineAddon.extend({
  // ...
  included() {
    this._super.included.apply(this, arguments);
    this.options.babel.plugins.push(...require('ember-cli-code-coverage').buildBabelPlugin());
  },
});

For app files in standalone addons (ember-cli-build.js):

let app = new EmberAddon(defaults, {
  babel: {
    plugins: [...require('ember-cli-code-coverage').buildBabelPlugin()]
  },
});

Add the following to your existing tests/test-helper.js:

import { forceModulesToBeLoaded, sendCoverage } from 'ember-cli-code-coverage/test-support';
import * as QUnit from 'qunit';

QUnit.done(async function() {
  forceModulesToBeLoaded();
  await sendCoverage();
});

For v2 Embroider native addons based on https://github.com/embroider-build/addon-blueprint blueprint:

// babel.config.cjs
module.exports = {
  plugins: [
    ['@babel/plugin-transform-typescript', { allExtensions: true, onlyRemoveTypeImports: true, allowDeclareFields: true }],
    '@embroider/addon-dev/template-colocation-plugin',
    ['babel-plugin-ember-template-compilation', { targetFormat: 'hbs', transforms: [] }],
    ['module:decorator-transforms', { runtime: 'globals' }],
    ...require('ember-cli-code-coverage').buildBabelPlugin(),
  ],
};

Coverage is collected by the test app test suite, so the app must set up tests/test-helper.js with sendCoverage() as shown in the Classic Ember CLI apps or Vite-based apps and addons sections.

For projects using @embroider/vite, add the coverage plugin to your Vite config.

This matches the ember-app-blueprint vite.config.mjs:

// vite.config.mjs
import { defineConfig } from 'vite';
import { extensions, classicEmberSupport, ember } from '@embroider/vite';
import { babel } from '@rollup/plugin-babel';
import { coveragePlugin } from 'ember-cli-code-coverage/vite';

const enableCoverage = process.env.COVERAGE === 'true';

export default defineConfig({
  plugins: [
    classicEmberSupport(),
    ember(),
    ...(enableCoverage ? coveragePlugin() : []),
    babel({
      babelHelpers: 'runtime',
      extensions,
    }),
  ],
});

No manual middleware wiring is needed — the addon auto-detects @embroider/vite and registers coverage middleware for you. See coverage collection under vite build + Testem for details and the manual override pattern.

This matches the ember-addon-blueprint vite.config.mjs:

// vite.config.mjs
import { defineConfig } from 'vite';
import { extensions, classicEmberSupport, ember } from '@embroider/vite';
import { babel } from '@rollup/plugin-babel';
import { coveragePlugin } from 'ember-cli-code-coverage/vite';

// For scenario testing
const isCompat = Boolean(process.env.ENABLE_COMPAT_BUILD);
const enableCoverage = process.env.COVERAGE === 'true';

export default defineConfig({
  plugins: [
    ...(isCompat ? [classicEmberSupport()] : []),
    ember(),
    ...(enableCoverage ? coveragePlugin() : []),
    babel({
      babelHelpers: 'inline',
      extensions,
    }),
  ],
  build: {
    rollupOptions: {
      input: {
        tests: 'tests/index.html',
      },
    },
  },
});

And the matching testem.cjs:

// testem.cjs
'use strict';

const { createViteTestemMiddleware } = require('ember-cli-code-coverage/testem');

if (typeof module !== 'undefined') {
  module.exports = {
    test_page: 'tests/index.html?hidepassed',
    cwd: 'dist-tests',
    disable_watching: true,
    launch_in_ci: ['Chrome'],
    launch_in_dev: ['Chrome'],
    browser_args: {
      Chrome: {
        ci: [
          process.env.CI ? '--no-sandbox' : null,
          '--headless',
          '--disable-dev-shm-usage',
          '--mute-audio',
          '--remote-debugging-port=0',
          '--window-size=1440,900',
        ].filter(Boolean),
      },
    },
    middleware: [createViteTestemMiddleware()],
  };
}

The coveragePlugin() function accepts the following options:

Example overriding only what you need. Note that exclude is a full replacement — repeat the defaults you want to keep:

coveragePlugin({
  exclude: [
    '**/node_modules/**',
    '**/tests/**',
    '**/mirage/**',
    '**/vendor/**',
  ],
  coverage: {
    reporters: ['html', 'lcov', 'json-summary'],
    coverageFolder: 'coverage',
  },
});

Instrumentation records hits in window.__coverage__, but reports are only written after the browser POSTs that payload to /write-coverage. Wire that up from ember-cli-code-coverage/test-support in tests/test-helper.js or tests/test-helper.ts (same pattern for either extension).

The following matches ember-app-blueprint tests/test-helper.ts, with coverage hooks added. Apps and addons both use this pattern.

// tests/test-helper.js — replace `my-app` with your package name / modulePrefix
import Application from 'my-app/app';
import config from 'my-app/config/environment';
import * as QUnit from 'qunit';
import { setApplication } from '@ember/test-helpers';
import { setup } from 'qunit-dom';
import { start as qunitStart, setupEmberOnerrorValidation } from 'ember-qunit';
import { forceModulesToBeLoaded, sendCoverage } from 'ember-cli-code-coverage/test-support';

export function start() {
  setApplication(Application.create(config.APP));

  setup(QUnit.assert);
  setupEmberOnerrorValidation();

  QUnit.done(async function () {
    try {
      forceModulesToBeLoaded();
    } catch (_e) {
      // Vite serves ESM; requirejs is not available — safe to ignore
    }
    await sendCoverage();
  });

  qunitStart();
}

If you use vite build + Testem (output to dist-tests or dist), the Vite dev server's configureServer hook from coveragePlugin() only runs under vite dev, not during a production-style test build. For this case the addon automatically detects @embroider/vite in your project's package.json and registers createViteTestemMiddleware() for you via its testemMiddleware hook — no extra testem.cjs configuration is required.

If you need to customize the middleware (e.g. point at a different project root or change the report output folder), you can register it manually from testem.cjs:

// testem.cjs
'use strict';

const { createViteTestemMiddleware } = require('ember-cli-code-coverage/testem');

module.exports = {
  test_page: 'tests/index.html?hidepassed',
  cwd: 'dist-tests',
  // ... other testem config
  middleware: [
    createViteTestemMiddleware({
      root: process.cwd(),                         // Project root (default: process.cwd())
      coverageFolder: 'coverage',                  // Output folder (default: 'coverage')
      reporters: ['html', 'lcov', 'json-summary'], // Reporter list (default shown)
    }),
  ],
};

Run with coverage enabled:

COVERAGE=true npm run test
# or
COVERAGE=true pnpm test

Coverage will only be generated when an environment variable is true (by default COVERAGE) and running your test command like normal.

For example:

COVERAGE=true ember test

If you want your coverage to work on both Unix and Windows, you can do this:

npm install cross-env --save-dev

and then:

cross-env COVERAGE=true ember test

When running with parallel set to true, the final reports can be merged by using ember coverage-merge. The final merged output will be stored in the coverageFolder.

If you intend to use ember test with the --path flag, you should generate the build with coverageEnvVar set as true. This is because the code is instrumented for coverage during the build.

For example:

COVERAGE=true ember build --environment=test --output-path=dist

followed by

COVERAGE=true ember test --path=dist

For Vite-based projects, TypeScript is handled natively by Vite/esbuild — no extra source-map configuration is required. The steps below apply only to classic ember-cli / Embroider builds.

Steps:

• in tsconfig.json

{
  "compilerOptions": {
    "inlineSourceMap": true,
    "inlineSources": true
  }
}

• in ember-cli-build.js

const app = new EmberApp(defaults, {
  babel: {
    sourceMaps: 'inline',
  },
  sourcemaps: {
    enabled: true,
    extensions: ['js'],
  },
});

• in package.json, use the latest 3.x release of ember-cli-code-coverage.

v3 ships hand-written TypeScript declarations for all public entry points (/babel, /vite, /istanbul, /testem, /test-support, /glimmer). See ARCHITECTURE.md for the full typed API.

• in ember-cli-build.js

  const app = new EmberApp(defaults, {
    'ember-template-imports': {
      inline_source_map: true,
    },
  });

Note: config/coverage.js is read by the classic Ember CLI / Embroider build pipeline only. The Vite plugin (ember-cli-code-coverage/vite) does not load config/coverage.js; configure it inline via coveragePlugin({ ... }) options. See the mapping table below and the Vite-based apps and addons section.

Configuration is optional. It should be put in a file at config/coverage.js (configPath configuration in package.json is honored). In addition to this you can configure Istanbul by adding a .istanbul.yml file to the root directory of your app (See https://github.com/istanbuljs/istanbuljs)

• coverageEnvVar: Defaults to COVERAGE. This is the environment variable that when set will cause coverage metrics to be generated.

• reporters: Defaults to ['lcov', 'html']. The json-summary reporter will be added to anything set here, it is required. This can be any reporters supported by Istanbul. Reporters can be configured with array-style syntax, for example, here are options to lcov with a different projectRoot: [['lcov', { projectRoot: '/packages/addon' }], 'html']

• excludes: Defaults to ['*/mirage/**/*']. An array of globs to exclude from instrumentation. Useful to exclude files from coverage statistics.

• extension: Defaults to ['.gjs', '.gts', '.js', '.ts', '.cjs', '.mjs', '.mts', '.cts']. Tell Istanbul to instrument only files with the provided extensions.

• coverageFolder: Defaults to coverage. A folder relative to the root of your project to store coverage results.

• parallel: Defaults to false. Should be set to true if parallel testing is being used for separate test runs, for example when using ember-exam with the --partition flag. This will generate the coverage reports in directories suffixed with _<random_string> to avoid overwriting other threads reports. These reports can be joined by using the ember coverage-merge command (potentially as part of the posttest hook in your package.json).

• modifyAssetLocation: Optional function that will allow you to override where a file actually lives inside of your project. See Advanced customization on how to use this function in practice.

  module.exports = {
    coverageEnvVar: 'COV'
  }

buildBabelPlugin() accepts an optional object. Most users don't need to pass anything — the function reads config/coverage.js automatically. These options are only useful when you need to override the defaults programmatically (e.g. in ember-cli-build.js or babel.config.cjs):

Values from config/coverage.js (excludes, coverageEnvVar, extension) take precedence over the built-in defaults when the file exists. The function returns [] when the coverage env var is not 'true'.

For Vite-based projects, translate each config/coverage.js key to its coveragePlugin() equivalent:

To work, this addon has to post coverage results back to a middleware at /write-coverage.

If you are using ember-cli-mirage you should add the following:

// in mirage/config.js

  this.passthrough('/write-coverage');
  this.namespace = 'api';  // It's important that the passthrough for coverage is before the namespace, otherwise it will be prefixed.

If you are using ember-cli-pretender you should add the following:

// where ever you set up the Pretender Server

  var server = new Pretender(function () {
    this.post('/write-coverage', this.passthrough);
  });

The forceModulesToBeLoaded function can potentially cause unintended side effects when executed. You can pass custom filter functions that allow you to specify which modules will be force loaded or not:

QUnit.done(async () => {
  // type will be either webpack and/or require
  forceModulesToBeLoaded((type, moduleName) => { return true; });
  await sendCoverage();
});

Under the hood, ember-cli-code-coverage attempts to "de-namespacify" paths into their real on disk location inside of project.root (ie give a namespaced path like lib/inrepo/components/foo.js would live in lib/inrepo/addon/components/foo.js). It makes some assumptions (where files live in in-repo addons vs app code for example) and sometimes those assumptions might not hold. Passing a function modifyAssetLocation in your configuration file will allow you to override where a file actually lives inside of your project. The returned string should be relative to your project root.

module.exports = {
  modifyAssetLocation(root, relativePath) {
    let appPath = relativePath.replace('my-project-name', 'app');

    // here is an example of saying that `app/components/foo.js` actually
    // lives in `lib/inrepo/app/components/foo.js` on disk.
    if (fs.existsSync(path.join(root, 'lib', 'inrepo', appPath))) {
      return path.join('lib', 'inrepo', appPath);
    }

    return false;
  },
};

• Node.js >= 20 is now required (was >= 18)
• Code has been reorganized into lib/ with modular entry points

The main entry point is fully backward compatible. If your setup looks like this, no changes are needed:

// ember-cli-build.js -- unchanged
const { buildBabelPlugin } = require('ember-cli-code-coverage');

// test-helper.js -- unchanged
import { forceModulesToBeLoaded, sendCoverage } from 'ember-cli-code-coverage/test-support';

v3 adds dedicated entry points for each concern. You can optionally use them for more explicit imports:

// Instead of:
const { buildBabelPlugin } = require('ember-cli-code-coverage');

// You can now also do:
const { buildBabelPlugin } = require('ember-cli-code-coverage/babel');

If you are migrating to Vite (via @embroider/vite), replace the ember-cli Babel plugin setup with the Vite plugin:

// vite.config.mjs
import { coveragePlugin } from 'ember-cli-code-coverage/vite';

export default defineConfig({
  plugins: [
    ember(),
    ...(process.env.COVERAGE === 'true' ? coveragePlugin() : []),
    babel({ extensions }), // see "Vite-based apps and addons" for babelHelpers
  ],
});

Coverage collection happens automatically, via one of two paths depending on how you run tests:

• Under vite dev, the coveragePlugin() registers a Vite server middleware at POST /write-coverage (Vite's configureServer hook).
• Under vite build + ember test (or any Testem-driven flow), the addon detects @embroider/vite in your package.json and auto-registers createViteTestemMiddleware() on the Testem express app via its testemMiddleware hook.

In both cases you do not need to wire any middleware manually. See Vite-based apps and addons for the full config (including the project-specific babelHelpers value) and for the manual override pattern.

All modules ship hand-written TypeScript declarations. Import types directly:

import type { BabelPluginOptions } from 'ember-cli-code-coverage/babel';
import type { VitePluginOptions } from 'ember-cli-code-coverage/vite';
import type { CoverageConfig } from 'ember-cli-code-coverage/istanbul';

This addon was inspired by ember-cli-blanket. The primary differences are that this addon uses Istanbul rather than Blanket for coverage and it instruments your application code as part of the build, when enabled.