Added unit test for CRON converter plugin

app/code/Magento/Cron/Test/Unit/Model/System/Config/Initial/ConverterTest.php

@@ -0,0 +1,89 @@
+<?php
+/**
+ * Copyright © Magento, Inc. All rights reserved.
+ * See COPYING.txt for license details.
+ */
+declare(strict_types=1);
+
+namespace Magento\Cron\Test\Unit\Model\System\Config\Initial;
+
+use Magento\Cron\Model\Groups\Config\Data as GroupsConfigModel;
+use Magento\Cron\Model\System\Config\Initial\Converter as ConverterPlugin;
+use Magento\Framework\App\Config\Initial\Converter;
+
+/**
+ * Class ConverterTest
+ *
+ * Unit test for \Magento\Cron\Model\System\Config\Initial\Converter
+ */
+class ConverterTest extends \PHPUnit\Framework\TestCase
+{
+    /**
+     * @var GroupsConfigModel|\PHPUnit_Framework_MockObject_MockObject
+     */
+    private $groupsConfigMock;
+
+    /**
+     * @var Converter|\PHPUnit_Framework_MockObject_MockObject
+     */
+    private $converterMock;
+
+    /**
+     * @var ConverterPlugin
+     */
+    private $converterPlugin;
+
+    /**
+     * @inheritdoc
+     */
+    protected function setUp()
+    {
+        $this->groupsConfigMock = $this->getMockBuilder(
+            GroupsConfigModel::class
+        )->disableOriginalConstructor()->getMock();
+        $this->converterMock = $this->getMockBuilder(Converter::class)->getMock();
+        $this->converterPlugin = new ConverterPlugin($this->groupsConfigMock);
+    }
+
+    /**
+     * Tests afterConvert method with no $result['data']['default']['system'] set
+     */
+    public function testAfterConvertWithNoData()
+    {
+        $expectedResult = ['test'];
+        $this->groupsConfigMock->expects($this->never())
+            ->method('get');
+
+        $result = $this->converterPlugin->afterConvert($this->converterMock, $expectedResult);
+
+        self::assertSame($expectedResult, $result);
+    }
+
+    /**
+     * Tests afterConvert method with $result['data']['default']['system'] set
+     */
+    public function testAfterConvertWithData()
+    {
+        $groups = [
+            'group1' => ['val1' => ['value' => '1']],
+            'group2' => ['val2' => ['value' => '2']]
+        ];
+        $expectedResult['data']['default']['system']['cron'] = [
+            'group1' => [
+                'val1' => '1'
+            ],
+            'group2' => [
+                'val2' => '2'
+            ]
+        ];
+        $result['data']['default']['system']['cron'] = '1';
+
+        $this->groupsConfigMock->expects($this->once())
+            ->method('get')
+            ->willReturn($groups);
+
+        $result = $this->converterPlugin->afterConvert($this->converterMock, $result);
+
+        self::assertEquals($expectedResult, $result);
+    }
+}