Queue implementation with using two stacks

QueueWithTwoStack.java

import java.util.NoSuchElementException;
import java.util.Stack;

/**
 * CLRS - Introduction to Algorithms Ex.10.1-6
 * 
 * Show how to implement a queue using two stacks. Analyze the running time of the queue operations
 * 
 * */
public class QueueWithTwoStack {

    private Stack<Integer> enqueueStack;
    private Stack<Integer> dequeueStack;

    public QueueWithTwoStack() {

        this.enqueueStack = new Stack<Integer>();
        this.dequeueStack = new Stack<Integer>();
    }

    public void enqueue(int item) {

        enqueueStack.push(item);
    }

    public int dequeue() {

        // right stack is not empty then return the next element
        if (!dequeueStack.isEmpty()) {

            return dequeueStack.pop();
        }

        // if right stack is empty then transfer all elements from
        // the left stack to the right stack. This will take O(n) time.
        if (!enqueueStack.isEmpty()) {

            while (!enqueueStack.isEmpty()) {

                dequeueStack.push(enqueueStack.pop());
            }

            return dequeueStack.pop();
        }

        // if both of stacks are empty means that our queue is empty
        throw new NoSuchElementException("Queue is empty");
    }

    public int size() {

        return enqueueStack.size() + dequeueStack.size();
    }

    public boolean isEmpty() {

        return enqueueStack.isEmpty() && dequeueStack.isEmpty();
    }
}

QueueWithTwoStackTest.java

import static org.junit.Assert.assertEquals;
import static org.junit.Assert.assertFalse;
import static org.junit.Assert.assertTrue;

import java.util.NoSuchElementException;

import org.junit.Before;
import org.junit.Test;

public class QueueWithTwoStackTest {

    private QueueWithTwoStack queue;

    @Before
    public void setUp() {

        queue = new QueueWithTwoStack();
    }

    @Test(expected = NoSuchElementException.class)
    public void dequeueFromEmptyQueue() {

        queue.dequeue();
    }

    @Test
    public void sizeTest() {

        for (int i = 0; i < 10; i++) {

            queue.enqueue(i);
        }

        assertEquals(10, queue.size());

        queue.dequeue();
        queue.dequeue();
        queue.dequeue();

        queue.enqueue(1);

        assertEquals(8, queue.size());
    }

    @Test
    public void testEnqueueAndDequeue() {

        for (int i = 0; i < 10; i++) {

            queue.enqueue(i);
        }

        int counter = 0;

        while (!queue.isEmpty()) {

            assertEquals(counter, queue.dequeue());
            counter++;
        }
    }

    @Test
    public void testIsEmpty() {

        assertTrue(queue.isEmpty());
    }

    @Test
    public void testNotEmpty() {

        queue.enqueue(5);

        assertFalse(queue.isEmpty());
    }
}