texmath-0.12.5: test/writer/tex/msub-10.test

<<< native
[ ESub (EIdentifier "S") (ENumber "5")
, ESymbol Rel "="
, EUnder
    False
    (ESub (EIdentifier "S") (ENumber "5"))
    (EPhantom (EIdentifier "t"))
]
>>> tex
S_{5} = \underset{\phantom{t}}{S_{5}}