texmath-0.12.5: test/writer/tex/munder-11.test

<<< native
[ EUnder False (EIdentifier "BASE") (EIdentifier "x")
, ESymbol Rel "="
, EUnder
    False
    (EIdentifier "BASE")
    (EGrouped
       [ EPhantom (ENumber "1")
       , EIdentifier "x"
       , EPhantom (ENumber "1")
       ])
]
>>> tex
\underset{x}{BASE} = \underset{\phantom{1}x\phantom{1}}{BASE}