      data-testname="aria-labelledby reference to element with default slotted text content"></button>

<label id="label3">
  <div id="host3">slotted</div>
</label>
<button id="labelled3"
        class="labelled"
        type="button"
        aria-labelledby="label3"
        data-expectedlabel="foo slotted bar"
        data-testname="aria-labelledby reference to element with slotted text content and aria-label on slot"></button>

<label id="label4">
  <div id="host4"></div>
</label>
<button id="labelled4"
 