magento-test/app/code/Magento/Checkout/Test/Mftf/ActionGroup/CheckoutSelectFlatRateShippingMethodActionGroup.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">
    <!-- Checkout select Flat Rate shipping method -->
    <actionGroup name="CheckoutSelectFlatRateShippingMethodActionGroup">
        <annotations>
            <description>Clicks on the 'Flat Rate' Shipping Method on the Storefront Checkout page.</description>
        </annotations>

        <conditionalClick selector="{{CheckoutShippingMethodsSection.checkShippingMethodByName('Flat Rate')}}" dependentSelector="{{CheckoutShippingMethodsSection.checkShippingMethodByName('Flat Rate')}}" visible="true" stepKey="selectFlatRateShippingMethod"/>
        <waitForPageLoad stepKey="waitForLoadingMaskForNextButton"/>
    </actionGroup>
</actionGroups>