magento-test/app/code/Magento/Payment/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="payment" translate="label" type="text" sortOrder="400" showInDefault="1" showInWebsite="1" showInStore="1">
            <label>Payment Methods</label>
            <tab>sales</tab>
            <resource>Magento_Payment::payment</resource>
            <group id="free" translate="label" type="text" sortOrder="30" showInDefault="1" showInWebsite="1" showInStore="1">
                <label>Zero Subtotal Checkout</label>
                <field id="active" translate="label" type="select" sortOrder="1" showInDefault="1" showInWebsite="1" canRestore="1">
                    <label>Enabled</label>
                    <source_model>Magento\Config\Model\Config\Source\Yesno</source_model>
                </field>
                <field id="order_status" translate="label" type="select" sortOrder="2" showInDefault="1" showInWebsite="1" canRestore="1">
                    <label>New Order Status</label>
                    <source_model>Magento\Sales\Model\Config\Source\Order\Status\Newprocessing</source_model>
                </field>
                <field id="payment_action" translate="label" type="select" sortOrder="3" showInDefault="1" showInWebsite="1" canRestore="1">
                    <label>Automatically Invoice All Items</label>
                    <source_model>Magento\Payment\Model\Source\Invoice</source_model>
                    <depends>
                        <field id="order_status" separator=",">processing</field>
                    </depends>
                </field>
                <field id="sort_order" translate="label" type="text" sortOrder="100" showInDefault="1" showInWebsite="1" canRestore="1">
                    <label>Sort Order</label>
                    <frontend_class>validate-number</frontend_class>
                </field>
                <field id="title" translate="label" type="text" sortOrder="1" showInDefault="1" showInWebsite="1" showInStore="1" canRestore="1">
                    <label>Title</label>
                </field>
                <field id="allowspecific" translate="label" type="allowspecific" sortOrder="50" showInDefault="1" showInWebsite="1" canRestore="1">
                    <label>Payment from Applicable Countries</label>
                    <source_model>Magento\Payment\Model\Config\Source\Allspecificcountries</source_model>
                </field>
                <field id="specificcountry" translate="label" type="multiselect" sortOrder="51" showInDefault="1" showInWebsite="1">
                    <label>Payment from Specific Countries</label>
                    <source_model>Magento\Directory\Model\Config\Source\Country</source_model>
                    <can_be_empty>1</can_be_empty>
                </field>
                <field id="model"></field>
            </group>
        </section>
    </system>
</config>