texmath-0.13.1.2: test/writer/mml/msup-03.test

<<< native
[ ESuper (ENumber "2") (ENumber "3")
, ESymbol Rel "="
, ESuper
    (ENumber "2")
    (ESuper (ENumber "3") (EPhantom (EIdentifier "fail")))
]
>>> mml
<?xml version='1.0' ?>
<math display="block" xmlns="http://www.w3.org/1998/Math/MathML">
  <mrow>
    <msup>
      <mn>2</mn>
      <mn>3</mn>
    </msup>
    <mo>=</mo>
    <msup>
      <mn>2</mn>
      <msup>
        <mn>3</mn>
        <mphantom>
          <mi>fail</mi>
        </mphantom>
      </msup>
    </msup>
  </mrow>
</math>