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);
    this.options.babel.plugins.push(...require('ember-cli-code-coverage').buildBabelPlugin());
  },
});

tests/test-helpers.js:

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

QUnit.done(async function() {
  forceModulesToBeLoaded();
  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

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 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 https://github.com/gotwarlost/istanbul#configuring)

• 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).

  module.exports = {
    coverageEnvVar: 'COV'
  }

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 can potientally cause unindented 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 will allow you to override where a file actually lives inside of your project. The returned string should be relative to your project root.

const app = new EmberApp(defaults, {
  'ember-cli-code-coverage': {
    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.