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npm version CI

Code coverage using Istanbul for Ember apps.


  • 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-cli-babel >= 6.0.0


  • ember install 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 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);


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

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


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

TypeScript integration


  • 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 specify latest available version
    devDependencies: {
      "ember-cli-code-coverage": "^1.0.0-beta.9"


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


  • 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.

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

  • 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'

Create a passthrough when intercepting all ajax requests in tests

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.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 () {'/write-coverage', this.passthrough);

Advanced customization


The forceModulesToBeLoaded function can potentially cause unintended side effects when executed. You can pass custom filter fuctions 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;


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.