magento-test/app/code/Magento/Backend/Test/Mftf/Section/AdminMessagesSection.xml

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

<sections xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
          xsi:noNamespaceSchemaLocation="urn:magento:mftf:Page/etc/SectionObject.xsd">
    <section name="AdminMessagesSection">
        <!-- Keep both sets of elements -->
        <!-- Set One - more specific, works for most of message blocks -->
        <element name="success" type="text" selector="#messages div.message-success"/>
        <element name="nthSuccess" type="text" selector=".message.message-success.success:nth-of-type({{n}})>div" parameterized="true"/>
        <element name="error" type="text" selector="#messages div.message-error"/>
        <element name="notice" type="text" selector=".message.message-notice.notice"/>
        <element name="messageByType" type="text" selector="#messages div.message-{{messageType}}" parameterized="true" />
        <element name="warning" type="text" selector="#messages div.message-warning"/>
        <element name="accessDenied" type="text" selector=".access-denied-page"/>
        <!-- Set Two - more generic, needed for message blocks in Product Import, Staging Update, etc -->
        <element name="successMessage" type="text" selector=".message-success"/>
        <element name="errorMessage" type="text" selector=".message.message-error.error"/>
        <element name="warningMessage" type="text" selector=".message-warning"/>
        <element name="noticeMessage" type="text" selector=".message-notice"/>
    </section>
</sections>