AssertionError: expected {} to be a function
<p>I'm getting a strange error while using Mocha with Chai for the first time. The only framework I've used before is Jasmine, if that should help you figure out what I'm doing wrong.</p>

<p>I'm simply trying to make sure my constructor doesn't throw an error. I've been able to reduce the code to this, still getting the error:</p>

<pre><code>class MyLib {
  constructor() {}
}

export default MyLib;
</code></pre>

<p>This is the test file:</p>

<pre><code>import chai from 'chai';
let { expect } = chai;

import MyLib from '../index';

describe('mylib-js', () =&gt; {
  describe('constructor', () =&gt; {
    it('should work', () =&gt; {
      expect(new MyLib()).to.not.throw();
    })
  });
});
</code></pre>

<p>This is the output from Mocha:</p>

<pre><code>d:\path\to\mylib-js&gt;mocha --require babel-core/register


  mylib-js
    constructor
      1) should work


  0 passing (23ms)
  1 failing

  1) mylib-js constructor should work:
     AssertionError: expected {} to be a function
      at Assertion.an (d:\path\to\mylib-js\node_modules\chai\lib\chai\core\assertions.js:169:10)

      at Assertion.assert (d:\path\to\mylib-js\node_modules\chai\lib\chai\utils\addChainableMethod.js:84:49)
      at Assertion.assertThrows (d:\path\to\mylib-js\node_modules\chai\lib\chai\core\assertions.js:1273:32)
      at Assertion.ctx.(anonymous function) [as throw] (d:\path\to\mylib-js\node_modules\chai\lib\chai\utils\addMethod.js:41:25)
      at Context.&lt;anonymous&gt; (test.js:10:4)
      at callFn (C:\Users\Myuser\AppData\Roaming\npm\node_modules\mocha\lib\runnable.js:315:21)
      at Test.Runnable.run (C:\Users\Myuser\AppData\Roaming\npm\node_modules\mocha\lib\runnable.js:308:7)
      at Runner.runTest (C:\Users\Myuser\AppData\Roaming\npm\node_modules\mocha\lib\runner.js:422:10)
      at C:\Users\Myuser\AppData\Roaming\npm\node_modules\mocha\lib\runner.js:533:12
      at next (C:\Users\Myuser\AppData\Roaming\npm\node_modules\mocha\lib\runner.js:342:14)
      at C:\Users\Myuser\AppData\Roaming\npm\node_modules\mocha\lib\runner.js:352:7
      at next (C:\Users\Myuser\AppData\Roaming\npm\node_modules\mocha\lib\runner.js:284:14)
      at Immediate._onImmediate (C:\Users\Myuser\AppData\Roaming\npm\node_modules\mocha\lib\runner.js:320:5)
</code></pre>

<p>I have no idea where it gets <code>{}</code> from in the error output. What is it trying to tell me?</p>