MCP-826: Use RabbitMQ for all consumers if AMQP is set in deployment config

- Add unit test;

Author: adifucan

lib/internal/Magento/Framework/MessageQueue/Test/Unit/DefaultValueProviderTest.php

@@ -0,0 +1,75 @@
+<?php
+/**
+ * Copyright © Magento, Inc. All rights reserved.
+ * See COPYING.txt for license details.
+ */
+declare(strict_types=1);
+
+namespace Magento\Framework\MessageQueue\Test\Unit;
+
+use Magento\Framework\App\DeploymentConfig;
+use Magento\Framework\MessageQueue\DefaultValueProvider;
+use PHPUnit\Framework\TestCase;
+
+class DefaultValueProviderTest extends TestCase
+{
+    /**
+     * @var DeploymentConfig
+     */
+    private $config;
+
+    /**
+     * @var DefaultValueProvider
+     */
+    private DefaultValueProvider $model;
+
+    /**
+     * @return void
+     */
+    protected function setUp(): void
+    {
+        $this->config = $this->getMockBuilder(DeploymentConfig::class)
+            ->disableOriginalConstructor()
+            ->getMock();
+        $this->model = new DefaultValueProvider('db', 'magento', $this->config);
+    }
+
+    /**
+     * @return void
+     */
+    public function testGetConnection(): void
+    {
+        $this->assertEquals('db', $this->model->getConnection());
+    }
+
+    /**
+     * @return void
+     *
+     */
+    public function testGetDefaultConnection(): void
+    {
+        $this->config->method('get')->willReturnMap(
+            [
+                ['queue/default_connection', null, 'test_connection'],
+            ]
+        );
+
+        $this->assertEquals('test_connection', $this->model->getConnection());
+    }
+
+    /**
+     * @return void
+     *
+     */
+    public function testGetAMQPConnection(): void
+    {
+        $this->config->method('get')->willReturnMap(
+            [
+                ['queue/default_connection', null, null],
+                ['queue/amqp', null, ['host' => '127.0.0.1', 'port' => '5672']]
+            ]
+        );
+
+        $this->assertEquals('amqp', $this->model->getConnection());
+    }
+}