Add Testing Fakes

[stevebauman]

Description

This PR introduces a testing Fake system, making it easy to test OAuth authentication flows without hitting real OAuth providers, and without having to use Mockery.

Usage

Consider the Socialite controller below:

class SocialiteController extends Controller
{
    public function redirect(string $provider)
    {
        return Socialite::driver($provider)->redirect();
    }

    public function callback(string $provider)
    {
        $socialiteUser = Socialite::driver($provider)->user();

        $user = User::firstOrCreate(
            ['email' => $socialiteUser->getEmail()],
            [
                'name' => $socialiteUser->getName(),
                "{$provider}_id" => $socialiteUser->getId(),
            ]
        );

        Auth::login($user);

        return redirect('/dashboard');
    }
}

Then, in our tests, we can utilize Socialite::fake($provider, $user) to initialize the fake and perform assertions:

use Laravel\Socialite\Socialite;
use Laravel\Socialite\Two\User;

test('user is redirected to github', function () {
    Socialite::fake('github');

    get('/auth/github/redirect')->assertRedirect('https://socialite.fake/github/authorize');
});

test('user can login with github', function () {
    $user = (new User)->map([
        'id' => 'github-123',
        'name' => 'John Doe',
        'email' => '[email protected]',
    ]);

    Socialite::fake('github', $fakeUser);

    get('/auth/github/callback')->assertRedirect('/dashboard');
    
    assertDatabaseHas(User::class, [
        'email' => $user->getEmail(),
        'name' => $user->getName(),
        'github_id' => $user->getId(),
    ]);
});

Let me know your thoughts!