add unit test for plugin

src/Plugin/HandleQueueMessageRejectPlugin.php

@@ -32,6 +32,7 @@ public function aroundReject(
     ): void {
         if (!$error) {
             $proceed($envelope, $requeue, $error);
+            return;
         }
 
         $shouldBeSavedForRetry = $this->isMessageShouldBeSavedForRetryService->execute($envelope);

src/Test/Unit/Plugin/HandleQueueMessageRejectPluginTest.php

@@ -0,0 +1,93 @@
+<?php
+
+declare(strict_types=1);
+
+namespace RunAsRoot\MessageQueueRetry\Test\Unit\Plugin;
+
+use Magento\Framework\MessageQueue\Envelope;
+use Magento\Framework\MessageQueue\QueueInterface;
+use PHPUnit\Framework\MockObject\MockObject;
+use PHPUnit\Framework\TestCase;
+use RunAsRoot\MessageQueueRetry\Plugin\HandleQueueMessageRejectPlugin;
+use RunAsRoot\MessageQueueRetry\Service\IsMessageShouldBeSavedForRetryService;
+use RunAsRoot\MessageQueueRetry\Service\SaveFailedMessageService;
+
+final class HandleQueueMessageRejectPluginTest extends TestCase
+{
+    private IsMessageShouldBeSavedForRetryService|MockObject $isMessageShouldBeSavedForRetryServiceMock;
+    private SaveFailedMessageService|MockObject $saveFailedMessageServiceMock;
+    private QueueInterface|MockObject $queueMock;
+    private HandleQueueMessageRejectPlugin $sut;
+    private bool $isProceedCalled;
+    private \Closure $testProceedFn;
+
+    public function setUp(): void
+    {
+        $this->isMessageShouldBeSavedForRetryServiceMock = $this->createMock(IsMessageShouldBeSavedForRetryService::class);
+        $this->saveFailedMessageServiceMock = $this->createMock(SaveFailedMessageService::class);
+        $this->queueMock = $this->createMock(QueueInterface::class);
+
+        $this->isProceedCalled = false;
+        $this->testProceedFn = fn () => $this->isProceedCalled = true;
+
+        $this->sut = new HandleQueueMessageRejectPlugin(
+            $this->isMessageShouldBeSavedForRetryServiceMock,
+            $this->saveFailedMessageServiceMock
+        );
+    }
+
+    public function testItShouldSaveFailedMessageAndNotProceed(): void
+    {
+        $testError = 'test error';
+
+        $this->isMessageShouldBeSavedForRetryServiceMock->expects($this->once())->method('execute')->willReturn(true);
+        $this->saveFailedMessageServiceMock->expects($this->once())->method('execute');
+        $this->queueMock->expects($this->once())->method('acknowledge');
+
+        $this->sut->aroundReject(
+            $this->queueMock,
+            $this->testProceedFn,
+            new Envelope('body'),
+            false,
+            $testError
+        );
+
+        self::assertFalse($this->isProceedCalled);
+    }
+
+    public function testItProceedIfMessageShouldNotBeSavedForRetry(): void
+    {
+        $testError = 'test error';
+
+        $this->isMessageShouldBeSavedForRetryServiceMock->expects($this->once())->method('execute')->willReturn(false);
+        $this->saveFailedMessageServiceMock->expects($this->never())->method('execute');
+
+        $this->sut->aroundReject(
+            $this->queueMock,
+            $this->testProceedFn,
+            new Envelope('body'),
+            false,
+            $testError
+        );
+
+        self::assertTrue($this->isProceedCalled);
+    }
+
+    public function testItProceedIfThereIsNoError(): void
+    {
+        $testEmptyError = '';
+
+        $this->saveFailedMessageServiceMock->expects($this->never())->method('execute');
+        $this->isMessageShouldBeSavedForRetryServiceMock->expects($this->never())->method('execute');
+
+        $this->sut->aroundReject(
+            $this->queueMock,
+            $this->testProceedFn,
+            new Envelope('body'),
+            false,
+            $testEmptyError
+        );
+
+        self::assertTrue($this->isProceedCalled);
+    }
+}