Ensure the done() callback is being called in this test (Mocha, Chai, Sinon)
<p>Looking at other questions, can't really find the cause of the problem. I am trying to import a module and test it using mocha. </p>

<pre><code>import chai, {
    expect
}
from 'chai';
import sinon from 'sinon';
import sinonChai from 'sinon-chai';
import System from 'systemjs';
import '../public/config.js';

chai.use(sinonChai);

describe('helperModule', () =&gt; {
    let module;

    before(function () {
        return System.import('./public/js/helper.js')
            .then((mod) =&gt; module = mod);
    });

    describe('Module loading', function () {
        it('should load', function(){
            expect(module.default).to.not.be.undefined;
        });
    });
});
</code></pre>

<p>I get the following error when running the <code>npm test</code> command.</p>

<pre><code>1) helperModule "before all" hook:
     Error: timeout of 2000ms exceeded. Ensure the done() callback is being
 called in this test.
</code></pre>

<p>Not really sure where to put the done callback. If you need any extra information about any packages I am using I will edit my question with them.</p>