### Question:
IntList { public static IntList catenate(IntList A, IntList B) { if (A == null) { return B; } IntList returnList = new IntList (A.first , null); IntList q = returnList; A = A.rest; while (A != null) { q.rest = new IntList(A.first, null); A = A.rest; q = q.rest; } q.rest = B; return returnList; } IntList(int first0, IntList rest0);  IntList(); static void dSquareList(IntList L); static IntList squareListIterative(IntList L); static IntList squareListRecursive(IntList L); static IntList dcatenate(IntList A, IntList B); static IntList catenate(IntList A, IntList B); @Override int hashCode(); static IntList of(Integer... args); boolean equals(Object x); @Override /** Outputs the IntList as a String. You are not expected to read * or understand this method. */ String toString(); public int first; public IntList rest; }### Answer:
@Test public void testCatenate() { IntList A = IntList.of(1, 2, 3); IntList B = IntList.of(4, 5, 6); IntList exp = IntList.of(1, 2, 3, 4, 5, 6); assertEquals(exp, IntList.catenate(A, B)); assertEquals(IntList.of(1, 2, 3), A); }