prox_equals(getBox("base0031").top - getBox("radical0031").top,
                           v1 + v2, epsilon,
                           "msqrt: vertical gap");
      assert_approx_equals(getBox("base0032").top - getBox("radical0032").top,
                           v1 + v2, epsilon,
                           "mroot: vertical gap");
    }, "RadicalExtraAscender");

    test(function() {
      assert_true(MathMLFeatureDetection.has_mspace());

      // Note: the size variants of U+221A in this font have widt