[FEATURE] Add FakeMailer inspired by Laravel

Classes/Core/Functional/Framework/Fakes/FakeMailer.php

@@ -0,0 +1,118 @@
+<?php
+
+declare(strict_types=1);
+
+namespace TYPO3\TestingFramework\Core\Functional\Framework\Fakes;
+
+use PHPUnit\Framework\Assert as PHPUnit;
+use Psr\EventDispatcher\EventDispatcherInterface;
+use Symfony\Component\Mailer\Envelope;
+use Symfony\Component\Mailer\Transport\TransportInterface;
+use Symfony\Component\Mime\RawMessage;
+use TYPO3\CMS\Core\Mail\Mailer;
+use TYPO3\CMS\Core\SingletonInterface;
+
+class FakeMailer extends Mailer implements SingletonInterface
+{
+    /**
+     * All the mails that have been sent.
+     */
+    private array $mails = [];
+
+    public function __construct(TransportInterface $transport = null, EventDispatcherInterface $eventDispatcher = null)
+    {
+        $GLOBALS['TYPO3_CONF_VARS']['MAIL']['transport'] = 'null';
+
+        parent::__construct($transport, $eventDispatcher);
+    }
+
+    /**
+     * Assert if an email was sent based on a truth-test callback.
+     */
+    public function assertSent(string $mail, callable|int $callback = null): void
+    {
+        if (is_numeric($callback)) {
+            $this->assertSentTimes($mail, $callback);
+            return;
+        }
+
+        $message = "The expected [{$mail}] mail was not sent.";
+
+        PHPUnit::assertTrue(
+            count($this->sent($mail, $callback)) > 0,
+            $message
+        );
+    }
+
+    /**
+     * Assert if an email was sent a number of times.
+     */
+    protected function assertSentTimes(string $mail, int $times = 1): void
+    {
+        $count = count($this->sent($mail));
+
+        PHPUnit::assertSame(
+            $times, $count,
+            "The expected [{$mail}] mail was sent {$count} times instead of {$times} times."
+        );
+    }
+
+    /**
+     * Determine if an email was not sent based on a truth-test callback.
+     */
+    public function assertNotSent(string $mail, callable $callback = null): void
+    {
+        $count = count($this->sent($mail, $callback));
+
+        PHPUnit::assertSame(
+            0,
+            $count,
+            "The unexpected [{$mail}] mail was sent."
+        );
+    }
+
+    /**
+     * Assert that no emails were sent.
+     */
+    public function assertNothingSent(): void
+    {
+        PHPUnit::assertEmpty($this->mails, 'Mails were sent unexpectedly.');
+    }
+
+    /**
+     * Get all the emails matching a truth-test callback.
+     */
+    public function sent(string $mail, callable $callback = null): array
+    {
+        if (! $this->hasSent($mail)) {
+            return [];
+        }
+
+        $callback = $callback ?: static fn () => true;
+
+        return array_filter($this->mailsOf($mail), static fn ($mail) => $callback($mail));
+    }
+
+    /**
+     * Determine if the given email has been sent.
+     */
+    public function hasSent(string $mail): bool
+    {
+        return count($this->mailsOf($mail)) > 0;
+    }
+
+    /**
+     * Get all the mailed emails for a given type.
+     */
+    protected function mailsOf(string $type): array
+    {
+        return array_filter($this->mails, static fn (RawMessage $mail) => $mail instanceof $type);
+    }
+
+    public function send(RawMessage $message, Envelope $envelope = null): void
+    {
+        parent::send($message, $envelope);
+
+        $this->mails[] = $message;
+    }
+}