Laravel 5.8 Nova login test Session is missing expected key [errors]

I am trying to write a simple unit test were I try to login with an invalid user in my Laravel Nova but I keep getting this error when I run the test:

Session is missing expected key [errors].

Failed asserting that false is true.

my test:

public function an_invalid_user_can_not_login()
{
    $user = factory(User::class)->create();

    $response = $this->post('/nova/login', [
        'email' => $user->email,
        'password' => 'invalid',
        '_token' => csrf_token(),
    ]);

    $response->assertSessionHasErrors();
    $this->assertGuest();
}

What am I doing wrong here?

via Chebli Mohamed