How does mocha do asynchronous tests in browser?

[deepinsource]

var a = 10;
setTimeout(function(){ a = 20; }, 0)  // don't change here

// What does mocha do here ???
// Does mocha have 'stop' method like qunit ?

assert(a === 20);

[tj]

it('should be async', function(done){
  doSomethingAsync(function(){
     assertSomething();
     done();
  });
});

[deepinsource]

// source code                   I don't want to chang it
function setState(el) {
  setTimeout(function(){
    el.addClass('active')
  }, 0)
}
--------------------------------------------------------------------------
// test code
it('', function(){
  var $el = $('document.body')
  setState($el)
  // how to test this without changing the source?
  // has something similar to qunit's stop method?
  assert($el.hasClass('active'))
})

[tj]

just setTimeout with 0 again and call done() in it, it'll fire after the other one

[tj]

not sure what stop() does in qunit, js has no sleep(), so i dont know what it would do

[deepinsource]

Thanks