 test(function() {
          // There are non-stretchy operators : the maximum of their base sizes
          // is used as the target size. In any case, operators remain at least
          // as large as their base size.

          element = document.getElementById("smaller_op");
          assert_approx_equals(element.getBoundingClientRect().width, .5 * emToPx, epsilon, "small width");
          assert_approx_equals(element.getBoundingClientRect().height, 1.5 * emToPx, epsilon, "height is the max(.5em, 1em)