magento-test/app/code/Magento/Checkout/Test/Mftf/ActionGroup/CheckoutSelectPurchaseOrderPaymentActionGroup.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="CheckoutSelectPurchaseOrderPaymentActionGroup">
        <annotations>
            <description>Selects the 'Purchase Order' Payment Method on the Storefront Checkout page.</description>
        </annotations>

        <arguments>
            <argument name="purchaseOrderNumber" type="string"/>
        </arguments>
        <waitForLoadingMaskToDisappear stepKey="waitForLoadingMask"/>
        <waitForPageLoad stepKey="waitForPageLoad"/>
        <remove keyForRemoval="checkCheckMoneyOption"/>
        <conditionalClick selector="{{CheckoutPaymentSection.purchaseOrderPayment}}" dependentSelector="{{CheckoutPaymentSection.purchaseOrderPayment}}" visible="true" stepKey="checkPurchaseOrderOption"/>
        <fillField selector="{{StorefrontCheckoutPaymentMethodSection.purchaseOrderNumber}}" userInput="{{purchaseOrderNumber}}" stepKey="fillPurchaseOrderNumber"/>
        <waitForLoadingMaskToDisappear stepKey="waitForLoadingMaskAfterPaymentMethodSelection"/>
    </actionGroup>
</actionGroups>