@chlab You might be able to find out by examining the official spark tests, which can be found here:
https://github.com/laravel/spark-tests/tree/3.0/tests
It looks like they have tests for v3, and v6 (change the branch). Other than that I haven't done tests with spark so don't know what else to suggest since I haven't tried it, but hopefully it will point you in the right direction.
Like here https://github.com/laravel/spark-tests/blob/6.0/tests/RegistrationTest.php
public function test_users_can_register()
{
$this->json('POST', '/register', [
'team' => 'Laravel',
'name' => 'Taylor Otwell',
'email' => '[email protected]',
'password' => 'secret',
'password_confirmation' => 'secret',
'terms' => true,
])->assertSuccessful();
$this->assertDatabaseHas('users', [
'email' => '[email protected]',
]);
$this->assertTrue(
User::where('email', '[email protected]')->first()->onGenericTrial()
);
}
Edit: it looks like they are using the actual url's and not route()'s.