title: How is helper 'andThen' in ember is different than traditional 'then'
body: <p>In the code below, I can use <code>then</code> instead of <code>andThen</code> and I see everything is running fine. So, what makes andThen special?</p>
  
  <pre><code>test('Clicked on the About page /about', function(assert) {
      visit('/')
      .click('a:contains("About")')
      .then(function(){
          assert.equal(currentURL(), '/about', 'SHould Navigate to about')
      })
  });
  
  test('Clicked on the About page /about', function(assert) {
      visit('/')
      .click('a:contains("About")')
      .andThen(function(){
          assert.equal(currentURL(), '/about', 'SHould Navigate to about')
      })
  });
  </code></pre>