Tests are added to this group either on `construct` by passing a fully-namespaced test class
or namespace string-based path, e.g.

{{{
$group = new Group(array('data' => array(
    'data\ModelTest',
    new \lithium\tests\cases\core\ObjectTest()
)));
}}}

Or they can be added programmatically:

{{{
$group->add('data\ModelTest');
}}}