magento-test/app/code/Magento/Email/Test/Mftf/ActionGroup/AssertEmailTemplateContentActionGroup.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="AssertEmailTemplateContentActionGroup">
        <arguments>
            <argument name="expectedContent" type="string" defaultValue="{{EmailTemplate.templateText}}"/>
        </arguments>

        <see userInput="{{expectedContent}}" stepKey="checkTemplateContainText"/>
    </actionGroup>
</actionGroups>