Prolog test cases seem to be broken. The integer value assigned to Result somehow gets converted into an array with duplicate members so you get error messages like

Assertion: [9,9]==[9] (forall bindings = [list1=[1,2,3],list2=[4,5,6],expected=9]) 

I do not know if you can edit the initial post after I replied to it, but you can post your code again in another reply

Noted. Not sure if I can actually edit this now though

Please use formatted code blocks when posting snippets of code.