在Symfony 5.0.2项目中，对新Mailer的测试失败，并显示

  

错误：在null上调用成员函数getSubject（）

电子邮件service和test基于symfonycast教程。

在var_dump($email);之后立即在服务中添加$email = ...;会显示object(Symfony\Bridge\Twig\Mime\TemplatedEmail)#24 (11) {...，这表明在服务中创建了一个真实的对象。

services.yaml：

    App\Services\EmailerService:
        $mailer: '@mailer'
        $senderAddress: '%app.sender_address%'

服务：

use Symfony\Bridge\Twig\Mime\TemplatedEmail;

class EmailerService
{
    private $mailer;
    private $sender;

    public function __construct($mailer,$senderAddress)
    {
        $this->mailer = $mailer;
        $this->sender = $senderAddress;
    }

    public function appMailer($mailParams)
    {
        $email = (new TemplatedEmail())
                ->from($this->sender)
                ->to($mailParams['recipient'])
                ->subject($mailParams['subject'])
                ->htmlTemplate($mailParams['view'])
                ->context($mailParams['context']);
        $this->mailer->send($email);
    }
}

测试：

use App\Services\EmailerService;
use PHPUnit\Framework\TestCase;
use Symfony\Component\Mailer\MailerInterface;

class MailerTest extends TestCase
{
    public function testSimpleMessage()
    {
        $symfonyMailer = $this->createMock(MailerInterface::class);
        $symfonyMailer->expects($this->once())
                ->method('send');

        $mailer = new EmailerService($symfonyMailer,'admin@bogus.info','admin@bogus.info');
        $mailParams = [
            'view' => 'Email/non_user_forgotten_password.html.twig','context' => ['supportEmail' => 'admin@bogus.info'],'recipient' => 'bborko@bogus.info','subject' => 'Test message',];
        $email = $mailer->appMailer($mailParams);

        $this->assertSame('Test message',$email->getSubject());
    }
}