Slack\User::getFirstName PHP Method

    public function getFirstName()
    {
        return isset($this->data['profile']['first_name']) ? $this->data['profile']['first_name'] : null;
    }

 public function testFirstName()
 {
     $firstName = $this->faker->firstName;
     $user = new User($this->client, ['profile' => ['first_name' => $firstName]]);
     $this->assertEquals($firstName, $user->getFirstName());
 }