You can check authorization with the ChecksAuthorization Trait
use ChecksAuthorization;
...
$this->assertRequestDenies(new Request($get, $post));
$this->assertRequestGrants(new Request($get, $post));
You can fake a currently authenticated usser and set its Rights:
public $fakeUserModel = \App\User::class;
...
$this->mockUser(array $rights);
$rights is an array with all the right keys of this user. You should set the fakeUserModel on the test class to resolve the user (which is \App\User by default)