Writing A Recursive Merge Sort Algorithm

I have this assignment to write a Merge Sort algorithm using recursion. To start I have a very tough time picturing what is happening when it comes to recursion, but I do understand how merge sorting works. At the moment I feel as though a very good portion of my code is correct, but I am having trouble with the recursion in the main method [ mergeSort(Queue<T> queue) ].

I have another 4 or so hours to pass in my assignment finished or not, and at this point I can honestly say I have no clue how to make my code work. I tried working through the problem on paper with a simple queue of size 3, but even that is a struggle. On paper my code works perfectly fine, so there is definitely something I am missing.

Below is what I have along with my JUnit test.

Java Code:

private Queue<T> output = new Queue<T>();
private Queue<T> output1 = new Queue<T>();
private Queue<T> output2 = new Queue<T>();
public Queue<T> mergeSort(Queue<T> queue) {
// TODO 1
if(queue.size() <= 1) {
return queue;

[Code] .....