magento-test/app/code/Magento/Elasticsearch6/etc/config.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_Store:etc/config.xsd">
    <default>
        <catalog>
            <search>
                <engine>elasticsearch6</engine>
                <elasticsearch6_server_hostname>localhost</elasticsearch6_server_hostname>
                <elasticsearch6_server_port>9200</elasticsearch6_server_port>
                <elasticsearch6_index_prefix>magento2</elasticsearch6_index_prefix>
                <elasticsearch6_enable_auth>0</elasticsearch6_enable_auth>
                <elasticsearch6_server_timeout>15</elasticsearch6_server_timeout>
                <elasticsearch6_minimum_should_match></elasticsearch6_minimum_should_match>
            </search>
        </catalog>
    </default>
</config>