magento-test/app/code/Magento/Customer/Test/Mftf/ActionGroup/AssertCustomerLoggedInActionGroup.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="AssertCustomerWelcomeMessageActionGroup">
        <annotations>
            <description>Validates that the Welcome message is present and correct, including the provided Customers Full Name.</description>
        </annotations>
        <arguments>
            <argument name="customerFullName" type="string"/>
        </arguments>

        <waitForPageLoad stepKey="waitForPageLoad"/>
        <see userInput="Welcome, {{customerFullName}}!" selector="{{StorefrontPanelHeaderSection.welcomeMessage}}" stepKey="verifyMessage"/>
    </actionGroup>
</actionGroups>