Merge sort not working

Question

so i've been trying to write a merge sort algorithm for linked lists for an assignment and i'm so fing close, but it's really frustrating me because it isn't working correctly. i have a sort and a merge method and i'm doing this recursively. can someone point out what i'm doing wrong?? it prints the elements (i've been testing with random strings) and even changes their order, but no luck on them actually being sorted. help is massively appreciated.
sort method:
public static <T extends Comparable<T>> void sort(ADTListInterface<T> list){  
     int s = list.size();
if (s<2)return;
MyLinkedList<T> listl = new MyLinkedList<T>();
MyLinkedList<T> listr = new MyLinkedList<T>();
int x=0;
for(; x<s/2; x++){
     listl.add(list.get(x));//add first half of list to new list
for(; x<s; x++){
     listr.add(list.get(x));//add rest of original list to new list
sort(listr);
sort(listl);
merge(listl, listr, list);     
merge method:
public static <T extends Comparable<T>> void merge(ADTListInterface<T> listl,ADTListInterface<T>
     listr,ADTListInterface<T> list){
     while(!listl.isEmpty() && !listr.isEmpty()){
          if(listl.get(0).compareTo(listr.get(0))<= 0){//select smaller element and put back in original list
               list.remove(listl.get(0));
               list.add(listl.get(0));
               listl.remove(0);
          else{
               list.remove(listr.get(0));
               list.add(listr.get(0));
               listr.remove(0);
     //if anything is left in remaining lists put elements into original list
     while(!listl.isEmpty()){
               list.remove(listl.get(0));
          list.add(listl.get(0));
          listl.remove(0);
     while(!listr.isEmpty()){
               list.remove(listr.get(0));
          list.add(listr.get(0));
          listr.remove(0);
}

Answer 1

i've been testing with random stringsIt would be better to test on specific things, eg from simple to complex. For example, test it with:
-an empty list
-"a"
-"a","b"
-"b", "a"
-"c","b","a"
continue until your sorting fails, then find out why it fails there and not on the previous test.