JHipster and Karma: Error when i launch npm run test:watch

I try to create my unit tests in my project with Jhipster 4.3 with Angular2.

But when i launch :

 npm run test:watch

I have an error when i open http://localhost:9876/# and i can't debug my test:

Chrome 57.0.2987 (Windows 10 0.0.0) ERROR
You need to include some adapter that implements __karma__.start method!

I Have two questions :

• It is normal if i have this error with Jhipster default configuration ?
• How can I debug my test with Karma and the preprocessors with breackpoint in the chrome dev toolbar ?

.

preprocessors: {'spec/entry.ts': ['webpack', 'sourcemap']}

Alternative solution :

Actually, i launch the @angular-cli alternative :

ng test

But i can't debug with breackpoint my test correctly.

Thanks for your help!