mock-updated-xblock.underscore

<li class="studio-xblock-wrapper is-draggable">
    <header class="xblock-header">
        <div class="header-details">
            <span class="xblock-display-name">Mock XBlock</span>
        </div>
        <div class="header-actions">
            <ul class="actions-list">
                <li class="sr action-item">No Actions</li>
            </ul>
        </div>
    </header>
    <article class="xblock-render">
        <div class="xblock xblock-student_view xmodule_display xmodule_VerticalModule"
             data-runtime-class="PreviewRuntime" data-init="XBlockToXModuleShim" data-runtime-version="1"
             data-type="None">
            <div class="mock-updated-content">Mock Update</div>
        </div>
    </article>
</li>