public function testCustomUser()
 {
     $webhook = new Webhook(new Url('https://hooks.slack.com/services/XXXXXXXXX/XXXXXXXXX/XXXXXXXXXXXXXXXXXXXXXXXXX'));
     $configWithoutCustomUser = new Config($webhook);
     $this->assertFalse($configWithoutCustomUser->hasCustomUser(), 'When there is no custom user the function hasCustomUser should return false');
     $user = new User(new Username('@pageon'));
     $configWithCustomUser = new Config($webhook, $user);
     $this->assertTrue($configWithCustomUser->hasCustomUser(), 'When there is a CustomUser the function hasCustomUser should return true');
     $this->assertEquals($user, $configWithCustomUser->getCustomUser(), 'The returned user should be the same as the provided user');
 }