ResultTest.php

<?php
/**
 * Copyright © Magento, Inc. All rights reserved.
 * See COPYING.txt for license details.
 */
namespace Magento\CatalogSearch\Block;

class ResultTest extends \PHPUnit\Framework\TestCase
{
    public function testSetListOrders()
    {
        /** @var $layout \Magento\Framework\View\Layout */
        $layout = \Magento\TestFramework\Helper\Bootstrap::getObjectManager()->create(
            \Magento\Framework\View\LayoutInterface::class
        );
        $layout->addBlock(\Magento\Framework\View\Element\Text::class, 'head');
        // The tested block is using head block
        /** @var $block \Magento\CatalogSearch\Block\Result */
        $block = $layout->addBlock(\Magento\CatalogSearch\Block\Result::class, 'block');
        $childBlock = $layout->addBlock(\Magento\Framework\View\Element\Text::class, 'search_result_list', 'block');

        $this->assertSame($childBlock, $block->getListBlock());
    }
}