JSFiddle - React, Tailwind, and code Playground

HTML

<script src="https://code.jquery.com/qunit/qunit-2.7.1.js"></script>
<link rel="stylesheet" href="https://code.jquery.com/qunit/qunit-2.7.1.css">
<div id="qunit"></div>
<div id="qunit-fixture"></div>

JavaScript

class Foo {
  constructor(a = 1) {
    this.a = a;
  }
}

Object.defineProperty(Foo.prototype, 'b', {
  enumerable: true,
  get() {
    return new Foo(this.a + 1);
  }
})

QUnit.test( "hello test", function( assert ) {
  assert.deepEqual(new Foo(), new Foo());
});