today is xmas

Holiday.php

<?php
/**
 * Created by PhpStorm.
 * User: joeychen
 * Date: 2018/9/24
 * Time: 下午 04:58
 */

namespace App;

use DateTime;

class Holiday
{
    public function SayXmas()
    {
        $today = $this->getToday();
        $todayDate = $today->format('md');
        if ($todayDate == '1224' || $todayDate == '1225') {
            return 'Merry Xmas';
        }
        else {
            return 'Today is not Xmas';
        }
    }

    /**
     * @return DateTime
     */
    protected function getToday()
    {
        $today = new DateTime();

        return $today;
    }
}

HolidayTest.php

<?php
/**
 * Created by PhpStorm.
 * User: joeychen
 * Date: 2018/9/24
 * Time: 下午 05:00
 */

namespace Tests {

    use App\FakeHoliday;
    use DateTime;
    use PHPUnit\Framework\TestCase;

    class HolidayTest extends TestCase
    {
        private $holiday;

        protected function setUp()
        {
            $this->holiday = new FakeHoliday();
        }

        public function test_today_is_xmas()
        {
            $this->givenToday(12, 25);
            $this->sayXmasShouldResponse('Merry Xmas');
        }

        public function test_today_is_not_xmas()
        {
            $this->givenToday(11, 25);
            $this->sayXmasShouldResponse('Today is not Xmas');
        }

        private function givenToday($month, $day)
        {
            $today = new DateTime();
            $today->setDate(2010, $month, $day);
            $this->holiday->setToday($today);
        }

        private function sayXmasShouldResponse($expected)
        {
            $response = $this->holiday->SayXmas();
            $this->assertEquals($expected, $response);
        }
    }
}

namespace App {

    class FakeHoliday extends Holiday
    {
        private $today;

        public function setToday($date)
        {
            $this->today = $date;
        }

        protected function getToday()
        {
            return $this->today;
        }
    }
}