magento-test/app/code/Magento/Customer/Test/Mftf/ActionGroup/StorefrontCustomerCreateAccountWithDateOfBirthActionGroup.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="StorefrontCustomerCreateAccountWithDateOfBirthActionGroup" extends="SignUpNewUserFromStorefrontActionGroup">
        <annotations>
            <description>EXTENDS: SignUpNewUserFromStorefrontActionGroup. Fills birthday field.</description>
        </annotations>
        <arguments>
            <argument name="dob" defaultValue="{{EN_US_DATE.short4DigitYear}}" type="string"/>
        </arguments>
        <fillField userInput="{{dob}}" selector="{{StorefrontCustomerCreateFormSection.dobField}}" after="fillLastName" stepKey="fillDob"/>
    </actionGroup>
</actionGroups>