magento-test/app/code/Magento/Elasticsearch/etc/adminhtml/system.xml

<?xml version="1.0"?>
<!--
/**
 * Copyright © Magento, Inc. All rights reserved.
 * See COPYING.txt for license details.
 */
-->
<config xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:noNamespaceSchemaLocation="urn:magento:module:Magento_Config:etc/system_file.xsd">
    <system>
        <section id="catalog">
            <group id="search">
                <!-- Elasticsearch 5.x -->
                <field id="elasticsearch5_server_hostname" translate="label" type="text" sortOrder="61" showInDefault="1">
                    <label>Elasticsearch Server Hostname</label>
                    <depends>
                        <field id="engine">elasticsearch5</field>
                    </depends>
                </field>
                <field id="elasticsearch5_server_port" translate="label" type="text" sortOrder="62" showInDefault="1">
                    <label>Elasticsearch Server Port</label>
                    <depends>
                        <field id="engine">elasticsearch5</field>
                    </depends>
                </field>
                <field id="elasticsearch5_index_prefix" translate="label" type="text" sortOrder="63" showInDefault="1">
                    <label>Elasticsearch Index Prefix</label>
                    <depends>
                        <field id="engine">elasticsearch5</field>
                    </depends>
                </field>
                <field id="elasticsearch5_enable_auth" translate="label" type="select" sortOrder="64" showInDefault="1">
                    <label>Enable Elasticsearch HTTP Auth</label>
                    <source_model>Magento\Config\Model\Config\Source\Yesno</source_model>
                    <depends>
                        <field id="engine">elasticsearch5</field>
                    </depends>
                </field>
                <field id="elasticsearch5_username" translate="label" type="text" sortOrder="65" showInDefault="1">
                    <label>Elasticsearch HTTP Username</label>
                    <depends>
                        <field id="engine">elasticsearch5</field>
                        <field id="elasticsearch5_enable_auth">1</field>
                    </depends>
                </field>
                <field id="elasticsearch5_password" translate="label" type="text" sortOrder="66" showInDefault="1">
                    <label>Elasticsearch HTTP Password</label>
                    <depends>
                        <field id="engine">elasticsearch5</field>
                        <field id="elasticsearch5_enable_auth">1</field>
                    </depends>
                </field>
                <field id="elasticsearch5_server_timeout" translate="label" type="text" sortOrder="67" showInDefault="1">
                    <label>Elasticsearch Server Timeout</label>
                    <depends>
                        <field id="engine">elasticsearch5</field>
                    </depends>
                </field>
                <field id="elasticsearch5_test_connect_wizard" translate="button_label" sortOrder="68" showInDefault="1">
                    <label/>
                    <button_label>Test Connection</button_label>
                    <frontend_model>Magento\Elasticsearch\Block\Adminhtml\System\Config\Elasticsearch5\TestConnection</frontend_model>
                    <depends>
                        <field id="engine">elasticsearch5</field>
                    </depends>
                </field>
                <field id="elasticsearch5_minimum_should_match" translate="label" type="text" sortOrder="93" showInDefault="1">
                    <label>Minimum Terms to Match</label>
                    <depends>
                        <field id="engine">elasticsearch5</field>
                    </depends>
                    <comment><![CDATA[<a href="https://docs.magento.com/user-guide/catalog/search-elasticsearch.html">Learn more</a> about valid syntax.]]></comment>
                    <backend_model>Magento\Elasticsearch\Model\Config\Backend\MinimumShouldMatch</backend_model>
                </field>
            </group>
        </section>
    </system>
</config>