Except basic test all other tests passes for me. please review tests.

Should pass Basic tests

a was [1,2], b was [1]: expected [] to deeply equal [ 2 ]

Random tests - 40 of them passed
Testing for arrayDiff([-13,-13,14,6,-9,-15,3,-16,-1,-11,8,4,-4,-11,-6,-10,-2,-10,-12,-10],[-13,-11,-13,-16,6,-9,14,-6,-10,3,-11,-15,-1,-10,-10,-2,-12])
Testing for arrayDiff([-6,0,-11,-5,7,4,-1,-1,-5,17,12,-19,2,-15,-19,-14,-16,-2,-16],[17,-11,-14,-16,-6,-19,-1,-15,-5,-2,-19,-1,0,4])
Testing for arrayDiff([5,-6],[])
Testing for arrayDiff([-16,-18,-15,-13,18,8,11,-16,14,-11,-8,-6,-4,-7,-16,1,-5,-4,-8,-19],[14,-4,-4,-8,-7,-15,-18,-8,1,18,11,-16])
Testing for arrayDiff([-17,-1],[-17])
Testing for arrayDiff([9,16,-10,12,4,-17,8,-20,14,-7,-3,7,-9,-11,-15,5,-16,-2,8],[-10,-20,8,-16,-9])
Testing for arrayDiff([8,12,2],[2])
Testing for arrayDiff([-8,-15,-12],[-15,-8])