JSFiddle - React, Tailwind, and code Playground

HTML

<ul id="results"></ul>

CSS

#results > li.pass { color: green; }
#results > li.fail { color: red; }

JavaScript

function assert(value, desc) {
  var li = document.createElement("li")
  
  li.className = value ? "pass" : "fail";
  li.appendChild(document.createTextNode(desc));
  document.getElementById("results").appendChild(li);
  console.log(document.getElementById("results").child)
  }
  
  window.onload = function() {
  assert(true, "The test suite is running.");
  assert(false, "Fail!");
  }