maxCommonSubExpr (Add (Opdi 2) (Opdi 42)) (Add (Opdi 2) (Opdi 42)) == [(Add (Opdi 2) (Opdi 42))]
maxCommonSubExpr (Add (Opdi 2) (Opdi 42)) (Mul (Opdi 2) (Opdi 42)) == [Opdi 2, Opdi 42]

expEqual (transform (Add (Opdi 2) (Opdi 42))) (Add (Opdi 2) (Opdi 42)) == True
expEqual (transform (Mul (Opdi 12) (Add (Opdi 2) (Opdi 42)))) (Add (Mul (Opdi 12) (Opdi 2)) (Mul (Opdi 12) (Opdi 42))) == True

exportAs (Sub (Mul (Add (Opdi 2) (Opdi 42)) (Opdi 3)) (Opdc 'b')) "Infix" == "(((2+42)*3)-b)"
exportAs (Sub (Mul (Add (Opdi 2) (Opdi 42)) (Opdi 3)) (Opdc 'b')) "Postfix" == "2 42 + 3 * b -"

isSearchTree (Node 42 "abc" (Leaf 27 "xyz") (Leaf 52 "uvw")) == True
isSearchTree (Node 42 "abc" (Leaf 43 "xyz") (Leaf 52 "uvw")) == False