magento-test/app/code/Magento/Tax/Test/Mftf/ActionGroup/AddCustomerTaxClassActionGroup.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">
    <!--Add Customer Tax Class-->
    <actionGroup name="AddCustomerTaxClassActionGroup">
        <annotations>
            <description>Adds the provided Customer Tax Class on the Admin Tax Rule creation/edit page.</description>
        </annotations>
        <arguments>
            <argument name="customerTaxClassName" type="string"/>
        </arguments>

        <!--Click Additional Settings-->
        <click stepKey="clickAdditionalSettings" selector="{{AdminTaxRulesSection.additionalSettings}}"/>
        <!--Click Product Add New Tax Class Button-->
        <click stepKey="clickCustomerAddNewTaxClassBtn" selector="{{AdminTaxRulesSection.customerAddNewTaxClass}}"/>
        <!--Fill field-->
        <fillField stepKey="fillCustomerNewTaxClass" selector="{{AdminTaxRulesSection.fieldCustomerNewTaxClass}}" userInput="{{customerTaxClassName}}"/>
        <!-- Save Product tax rate -->
        <click stepKey="saveProdTaxRate" selector="{{AdminTaxRulesSection.saveCustomerNewTaxClass}}"/>
    </actionGroup>
</actionGroups>