Scala problem

Test score: 5/6

Test testSimplify1 failed:
Expected
Or(Or(Or(And(Atom(x1),And(Not(Atom(x2)),Not(Atom(x3)))),Impl(And(Atom(x3),Atom(x4)),Atom(x1))),Equiv(Atom(x2),Or(Atom(x1),Atom(x2)))),Or(Not(Atom(x4)),Or(Not(Atom(x3)),Not(Atom(x4)))))
but got
Or(Or(Or(And(Atom(x1),Not(Or(Atom(x2),Not(Not(Atom(x3)))))),Impl(Not(Or(Not(Atom(x3)),Not(Atom(x4)))),Atom(x1))),Equiv(Atom(x2),Or(Atom(x1),Atom(x2)))),Not(And(Atom(x4),Not(Not(Not(Not(And(Atom(x3),Atom(x4)))))))))