Simple JS Assert Unit Testing function (via http://net.tutsplus.com/tutorials/javascript-ajax/quick-tip-quick-and-easy-javascript-testing-with-assert/)

script.js

var output = document.getElementById('output');  
  
function assert( outcome, description ) {  
    var li = document.createElement('li');  
    li.className = outcome ? 'pass' : 'fail';  
    li.appendChild( document.createTextNode( description ) );  
      
    output.appendChild(li);  
};

// Useage:
function add(num1, num2) {  
    return num1 + num2;  
}
  
var result = add(5, 20);  
assert( result == 24, 'Checking the add function');  
  
// OR  
assert( add( 5, 20 ) == 24, 'Checking the add function');