Ember: how to get coverage on the actual code, not the transpiled code

I'm trying to set up CI on existing projects, some use CoffeeScript, some use ES6 syntax. But I can't find a way to get a proper code coverage on the actual code. All I have is the coverage on the transpiled code and it seems I can't even post that to CodeClimate.

I tried:

• ember-cli-blanket: found on stackoverflow here. It gives result on the transpiled sources only:

  In fact, there is current no direct mapping between the es6 module names in the lcov output and the original input files.

• ember-cli-code-coverage: simpler but still run on the transpiled sources
• karma: (the link goes to a tutorial for Ember & karma) here PhantomJS complaints about ES6 syntax "import" (which is normal).
  • I tried to use a pre-processor to transpile the code.
  • There are a lot of possible things to do with browserify, webpack, etc... but I didn't figure out how to set up anything correctly.
  • I found this gist that could be interesting because it combines karma, browserify, babelify, Istanbul and PhantomJS, only qunit is missing. But I didn't succeeded to make anything work.