Strange behaviour using mocha and chai for unit testing

I m actually unit testing my little library and I m facing a problem with async tests.

In fact, when I try to run my test using the done function (in the "it" block), I've got a time out.

  beforeEach(function() {
    _componentInstance = new ComponentLoader();
  });

describe('FindComponent function with path and no exclusion',function(){
    this.timeout(15000);
    it('Should return a promise with an array result',function(done){
      _componentInstance.findComponent('./dist/lib/component/*').then(function(result){
        console.log(result) // gives the good resultset
        expect(result[0]).to.equals('./dist/lib/component/testComponentLoaderfzfzf.js'); // this file doesn't exist, I need to fail this test
        done(); // got a timeout after 15 secs
      });
    });
  });

When I try to console log the promise resultset, it works great, I have the list of file in the concerned directory.

But when I try to test using expect with chai, I've got a timeout...

I dont know what is going wrong there.