magento-test/app/code/Magento/Email/Test/Mftf/ActionGroup/PreviewFromGridEmailTemplateActionGroup.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="PreviewFromGridEmailTemplateActionGroup" extends="FindEmailTemplateActionGroup">
        <arguments>
            <argument name="template" defaultValue="EmailTemplate"/>
        </arguments>

        <click selector="{{AdminEmailTemplateIndexSection.templateActionByName(template.templateName)}}" stepKey="clickPreviewTemplate"/>
        <wait time="3" stepKey="waitForWindow"/>
        <switchToNextTab after="waitForWindow" stepKey="switchToNewOpenedTab"/>
        <seeInCurrentUrl url="{{AdminEmailTemplatePreviewPage.url}}" after="switchToNewOpenedTab" stepKey="seeWindowCurrentUrl"/>
        <seeElement selector="{{AdminEmailTemplatePreviewSection.iframe}}" after="seeWindowCurrentUrl" stepKey="seeIframeOnPage"/>
        <switchToIFrame userInput="preview_iframe" after="seeIframeOnPage" stepKey="switchToIframe"/>
        <waitForText userInput="{{template.templateText}}" after="switchToIframe" stepKey="waitForText"/>
    </actionGroup>
</actionGroups>