[background-position-y-valid.html]
  [e.style['background-position-y'\] = "y-start" should set the property value]
    expected: FAIL

  [e.style['background-position-y'\] = "0.5em, y-start, y-end" should set the property value]
    expected: FAIL

  [e.style['background-position-y'\] = "y-end" should set the property value]
    expected: FAIL