How to test a controller function in Laravel

I have an index() and save() function in my UserController.php, it's like this:

    public function index()
    {
        $users = Users::all();
        return $users;
    }

    public function save(Request $request)
    {
        $firstname = $request->txtFirstName;
        $lastname = $request->txtLastName;
        $email = $request->txtEmail;
        $username = $request->txtUsername;
        $password = $request->txtPassword;

        $users = new Users();
        $users->firstname = $firstname;
        $users->lastname = $lastname;
        $users->email = $email;
        $users->username = $username;
        $users->password = $password;
        $users->save();

    }

I want to properly test this two functions using PHPUnit by Laravel. So far, I've managed to test the save function but only with assertStatus() method. Any suggestions?