How do I write unit tests for a REST API built in Slim Framework?

I have an API built in Slim like this:

    $app->group('/'.$endpoint, function () use ($app, $endpoint) {        $handler = Api\Rest\Handlers\Factory::load($endpoint);        if (is_null($handler)) {            throw new \Exception('No REST handler found for '.$endpoint);        }        $app->get('(/:id)', function ($id) use ($app, $handler) {            echo json_encode($handler->get($id));        });        $app->post('', function () use ($app, $handler) {            echo json_encode($handler->post($app->request->post()));        });        $app->put(':id', function ($id) use ($app, $handler) {            echo json_encode($handler->put($id, $app->request->put()));        });        $app->delete(':id', function ($id) use ($app, $handler) {            echo json_encode($handler->delete($id));        });    });

$endpoint is a string, for example 'user';

How do I go about writing unit tests for it?

Ideally;

class RestUserTest extends PHPUnitFrameworkTestCase {    public function testGet()     {        $slim = ''; // my slim app        // set route 'api/user/1' with method GET        // invoke slim        // ensure that what we expected to happen did    }}

(The REST handler class would make it trivial to mock the results that would ordinarily be backed by a DB.)

It's the nitty gritty of how to spoof the request into Slim that I don't know how to do.