t_approx_equals(element.getBoundingClientRect().height, tallest_base_size, epsilon, "height is the max(.5em, 1em, 2em)");

          element = document.getElementById("big_vertical");
          assert_approx_equals(element.getBoundingClientRect().width, 2 * emToPx, epsilon, "large width");
          assert_approx_equals(element.getBoundingClientRect().height, tallest_base_size, epsilon, "height is the max(.5em, 1em, 2em)");

      }, `Only operators with a stretchy property and block stretch axis.`);

     