How to Testing the insert of User With SYMFONY 4

I'm beginner and i want to test inserting user using TestUnit

I have started with this code and i want your help to complete it //App/tests/Controller/UserController

class UserTest extends KernelTestCase
{
    public function testUser()
    { $user = new User();
    $user->setName("Test name");
    $user->setEmail("test@test.com");
        $entityManager->persist($user);
        $entityManager->flush();

// what add here to complete the test ( if the user is flushed or not for example)