我在Symfony 6项目的一个自定义类中使用Symfony mailer，通过类的构造函数中的类型提示使用自动装配，如下所示：

class MyClass {
        public function __construct(private readonly MailerInterface $mailer) {}

        public function sendEmail(): array
        {
            // Email is sent down here
            try {
                $this->mailer->send($email);
            
                return [
                    'success' => true,
                    'message' => 'Email sent',
                ];
            } catch (TransportExceptionInterface $e) {
                return [
                    'success' => false,
                    'message' => 'Error sending email: ' . $e,
                ];
            }
        }
    }

在控制器中调用sendEmail()方法，一切正常。
现在我想测试TransportException是否被正确处理，为此我需要邮件程序在我的测试中抛出TransportException，然而，这并不像我希望的那样工作。

注意：我不能通过传递无效的电子邮件地址来引发异常，因为sendMail方法只允许有效的电子邮件地址。

我尝试过的事情：

1）使用模拟邮件

// boot kernel and get Class from container
$container = self::getContainer();
$myClass = $container->get('App\Model\MyClass');

// create mock mailer service
$mailer = $this->createMock(Mailer::class);
$mailer->method('send')
        ->willThrowException(new TransportException());
$container->set('Symfony\Component\Mailer\Mailer', $mailer);

事实证明，我不能模拟Mailer类，因为它是final。

2）使用模拟（或存根）MailerInterface

// create mock mailer service
$mailer = $this->createStub(MailerInterface::class);
$mailer->method('send')
        ->willThrowException(new TransportException());
$container->set('Symfony\Component\Mailer\Mailer', $mailer);

没有错误，但没有抛出异常。似乎邮件服务没有被替换。

3）使用自定义MailerExceptionTester类

// MailerExceptionTester.php
<?php

namespace App\Tests;

use Symfony\Component\Mailer\Envelope;
use Symfony\Component\Mailer\Exception\TransportException;
use Symfony\Component\Mailer\MailerInterface;
use Symfony\Component\Mime\RawMessage;

/**
 * Always throws a TransportException
 */
final class MailerExceptionTester implements MailerInterface
{
    public function send(RawMessage $message, Envelope $envelope = null): void
    {
        throw new TransportException();
    }
}

在测试中：

// create mock mailer service
$mailer = new MailerExceptionTester();
$container->set('Symfony\Component\Mailer\Mailer', $mailer);

结果与2）相同

4）尝试替换MailerInterface服务而不是Mailer

// create mock mailer service
$mailer = $this->createMock(MailerInterface::class);
$mailer->method('send')
        ->willThrowException(new TransportException());
$container->set('Symfony\Component\Mailer\MailerInterface', $mailer);

错误信息：Symfony\Component\DependencyInjection\Exception\InvalidArgumentException: The "Symfony\Component\Mailer\MailerInterface" service is private, you cannot replace it.

5）将MailerInterface设置为公共

// services.yaml
services:
    Symfony\Component\Mailer\MailerInterface:
        public: true

Error: Cannot instantiate interface Symfony\Component\Mailer\MailerInterface

6）为MailerInterface添加别名

// services.yaml
services:
    app.mailer:
        alias: Symfony\Component\Mailer\MailerInterface
        public: true

错误信息：Symfony\Component\DependencyInjection\Exception\InvalidArgumentException: The "Symfony\Component\Mailer\MailerInterface" service is private, you cannot replace it.
如何在测试中替换autowired MailerInterface服务？