texmath-0.12.5: test/writer/eqn/mrow-02.test
<<< native [ ESuper (EIdentifier "x") (ENumber "2") , ESymbol Rel "=" , ESuper (EIdentifier "x") (ENumber "2") ] >>> eqn x sup 2 = x sup 2
<<< native [ ESuper (EIdentifier "x") (ENumber "2") , ESymbol Rel "=" , ESuper (EIdentifier "x") (ENumber "2") ] >>> eqn x sup 2 = x sup 2