   name: '--length-calc-reset',
    syntax: '<length>',
    initialValue: '0px',
    inherits: false
  });
  let element = document.getElementById("element");
  element.style = 'font-size: 11px; --length-calc: calc(10em + 10px); --unregistered:var(--length-calc-reset); --length-calc-reset: var(--length-calc)';
  let cs = getComputedStyle(element);
  for (let prop of ["--length-calc", "--length-calc-reset", "--unregistered"]) {
    assert_equals(cs.getPropertyValue(prop), "120px", "Should resolve properly: "