Tests the addition of libraries through the #attached['library'] property.
function testAttachedLibrary() {
$element['#attached']['library'][] = array(
'system',
'farbtastic',
);
drupal_render($element);
$scripts = drupal_get_js();
$this
->assertTrue(strpos($scripts, 'misc/farbtastic/farbtastic.js'), 'The attached_library property adds the additional libraries.');
}