= ch_ref.getBoundingClientRect().width;
  let ch_test = document.getElementById("ch_test");
  let ch_length = ch_test.x.baseVal[0];

  test(() => {
    assert_equals(ch_length.unitType, SVGLength.SVG_LENGTHTYPE_UNKNOWN);
    assert_approx_equals(ch_length.value, ref_width, 0.1);
  }, "ch unit in SVGLength");

  test(() => {
    ch_length.value = ref_width * 4;
    assert_approx_equals(ch_length.valueInSpecifiedUnits, 40, 0.3);
    ch_length.value = ref_width;
    assert_approx_equals(ch_length.value, ref_wi