magento-test/app/code/Magento/Checkout/Test/Mftf/ActionGroup/CheckoutPlaceOrderActionGroup.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">
    <actionGroup name="CheckoutPlaceOrderActionGroup">
        <annotations>
            <description>Clicks on 'Place Order'. Validates that the provided Order ID and Email You messages are present and correct.</description>
        </annotations>
        <arguments>
            <argument name="orderNumberMessage"/>
            <argument name="emailYouMessage"/>
        </arguments>

        <waitForPageLoad stepKey="waitForPageLoad"/>
        <waitForElementVisible selector="{{CheckoutPaymentSection.placeOrder}}" time="30" stepKey="waitForPlaceOrderButton"/>
        <waitForElementClickable selector="{{CheckoutPaymentSection.placeOrder}}" stepKey="waitForPlaceOrderButtonClickable"/>
        <click selector="{{CheckoutPaymentSection.placeOrder}}" stepKey="clickPlaceOrder"/>
        <waitForPageLoad stepKey="waitForOrderPlaced"/>
        <waitForElementVisible selector="{{CheckoutSuccessMainSection.success}}" stepKey="waitForSuccess"/>
        <see selector="{{CheckoutSuccessMainSection.success}}" userInput="{{orderNumberMessage}}" stepKey="seeOrderNumber"/>
        <see selector="{{CheckoutSuccessMainSection.success}}" userInput="{{emailYouMessage}}" stepKey="seeEmailYou"/>
    </actionGroup>
</actionGroups>