<div>
  <div metal:define-macro="test1">
    t1.v1:<span metal:define-slot="val1">test1: val1 should go here</span>
  </div>

  <div metal:define-macro="test2">
    t2.v1:<span metal:define-slot="val1">test2: val1 should go here</span>
    t2.v2:<span metal:define-slot="val2">test2 OK: unfilled val2</span>
  </div>

  <div metal:use-macro="test1">
    <div metal:fill-slot="val2">test1: unused invalid val2</div>
    <div metal:fill-slot="val1"  tal:omit-tag="">
      <div metal:use-macro="test2">
      <span metal:fill-slot="val1">OK: filled from test2/val1</span>
      </div>
    </div>
  </div>

</div>