Junit testing with random number

I am new to testing. I am using netbeans.

I have college assignment for junit testing but i am not so sure how should i test random number method. My question is how should I test below method?

/**
     * Method will generate a set of integers between the minimum and maximum of
     * the requested size. If the uniqueElements is true the set will consist of
     * unique integer values
     *
     * @param size the number of elements for the array
     * @param minimum the lower value of the range of integers to generate
     * @param maximum the upper value of the range of integers to generate
     * @param uniqueElements flag for unique values
     * @return
     */
    public static ArrayList<Integer> createSet(int size, int minimum, int maximum, boolean uniqueElements) {
        boolean filled = false;
        int i = 0;
        ArrayList<Integer> arraySet = null;
        if (size > 0) {
            arraySet = new ArrayList<Integer>();
            boolean isUnique = false;
            while (!filled) {
                int randi = (int) (Math.random() * (maximum - minimum)) + minimum;
// C        isu = true;
// C       for (int j = 0; j < i && u; j++) {
// ** NEED &=  isu = randi != A.get(j);
// C       }
//
//        if (isu || !u) {
//          A.add(randi);
//          i++;
//        }
                isUnique = true;
                for (int j = 0; j < i && uniqueElements; j++) {
                    isUnique = randi != arraySet.get(j);
                }

                if (isUnique || !uniqueElements) {
                    arraySet.add(randi);
                    i++;
                }

                filled = (i == size);
            }
        }
        return arraySet;
    }

For this assignment professor told me that cover 100% code coverage. I am not sure how should i Do that?

I created this test case

/**
     * Test of createSet method, of class ArraySetUtilities.
     */
    @Test(timeout = 5000)
    public void testCreateSet() {

        System.out.println("createSet");
        int size = 0;
        int minimum = 0;
        int maximum = 0;
        boolean uniqueElements = true;
        ArrayList<Integer> expResult = null;
        ArrayList<Integer> result = ArraySetUtilities.createSet(size, minimum, maximum, uniqueElements);
        assertEquals(expResult, result);

    }

Thank you in advance