");

          element = document.getElementById("bigger_op");
          assert_approx_equals(element.getBoundingClientRect().width, 2 * emToPx, epsilon, "large width");
          assert_approx_equals(element.getBoundingClientRect().height, 2 * emToPx, epsilon, "height is the max(1em, 2em)");

      }, `Operators smaller and larger than non-stretchy siblings.`);

      test(function() {
          element = document.getElementById("core_operator_1");
          assert_approx_equals(element.getBoundingClientRe