magento-test/app/code/Magento/Checkout/Test/Mftf/ActionGroup/GuestCheckoutFillNewBillingAddressActionGroup.xml

<?xml version="1.0" encoding="UTF-8"?>
<!--
 /**
  * Copyright © Magento, Inc. All rights reserved.
  * See COPYING.txt for license details.
  */
-->

<actionGroups xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
              xsi:noNamespaceSchemaLocation="urn:magento:mftf:Test/etc/actionGroupSchema.xsd">
    <!-- Guest checkout filling billing section -->
    <actionGroup name="GuestCheckoutFillNewBillingAddressActionGroup">
        <annotations>
            <description>Fills in the provided Customer and Address details on the Storefront Checkout page.</description>
        </annotations>
        <arguments>
            <argument name="customerVar"/>
            <argument name="customerAddressVar"/>
        </arguments>

        <fillField selector="{{CheckoutShippingSection.email}}" userInput="{{customerVar.email}}" stepKey="enterEmail"/>
        <waitForPageLoad stepKey="waitForLoading3"/>
        <fillField selector="{{CheckoutPaymentSection.guestFirstName}}" userInput="{{customerVar.firstname}}" stepKey="enterFirstName"/>
        <fillField selector="{{CheckoutPaymentSection.guestLastName}}" userInput="{{customerVar.lastname}}" stepKey="enterLastName"/>
        <fillField selector="{{CheckoutPaymentSection.guestStreet}}" userInput="{{customerAddressVar.street[0]}}" stepKey="enterStreet"/>
        <fillField selector="{{CheckoutPaymentSection.guestCity}}" userInput="{{customerAddressVar.city}}" stepKey="enterCity"/>
        <selectOption selector="{{CheckoutPaymentSection.guestRegion}}" userInput="{{customerAddressVar.state}}" stepKey="selectRegion"/>
        <fillField selector="{{CheckoutPaymentSection.guestPostcode}}" userInput="{{customerAddressVar.postcode}}" stepKey="enterPostcode"/>
        <fillField selector="{{CheckoutPaymentSection.guestTelephone}}" userInput="{{customerAddressVar.telephone}}" stepKey="enterTelephone"/>
    </actionGroup>
</actionGroups>