@Test
    public void testMultipleValues() {
        int valuerange = 20;

        final int num_of_operations = 2500;  // for insert and remove
        ArrayList<String> OperationSequence = new ArrayList<String>();

        System.out.println("----------------------------------------------------------");
        System.out.println("testMultipleValues: Checking Integrity after insert/remove");
        System.out.println("----------------------------------------------------------");
        for (int i = 0; i < num_of_operations; i++) {

            boolean check = false;

            StringBuilder sbTreeBefore = null;
            StringBuilder sbTreeAfter = null;


            sbTreeBefore = display();
            int val = (int) (Math.random() * valuerange);
            try {
                if (tree.insertNode(val, (float) val)) {
                    OperationSequence.add(String.format(" I:%02d", val));
                } else OperationSequence.add(String.format("(I:%02d)", val));
            } catch (Exception ex) {
                fail(".insertNode() raised an exception: " + ex);
            }
            sbTreeAfter = display();


            check = checkAVLIntegrity();
            String strError = " of AVL tree broken after multiple insert/remove (number of operations processed: " + i + "/" + num_of_operations + ")\n\t"
                    + "--> Insert/Remove sequence (I...Insert; R...Remove; operation in brackets \"()\" was unsuccessful because of duplicate or not existing node; the very last operation caused the error):\n\t"
                    + "    ---------------------------------------------------------------------------------------------\n\t"
                    + OperationSequence + "\n\t"
                    + "\nTree before insert:\n\t" + sbTreeBefore.toString() + "\n\n\tTree after insert:" + sbTreeAfter.toString() + "\n\t";


            assertTrue(check, "Integrity" + strError);
            assertTrue(tree.getTreeHeight() <= (1.44 * (Math.log(tree.getSize() + 2) / Math.log(2)) - 0.328), "Height" + strError);


            sbTreeBefore = display();
            val = (int) (Math.random() * valuerange);
            try {
                if (tree.removeNode(val)) {
                    OperationSequence.add(String.format(" R:%02d", val));
                } else OperationSequence.add(String.format("(R:%02d)", val));
            } catch (Exception ex) {
                fail(".removeNode() raised an exception: " + ex);
            }
            sbTreeAfter = display();

            check = checkAVLIntegrity();

            strError = " of AVL tree broken after multiple insert/remove (number of operations processed: " + i + "/" + num_of_operations + ")\n\t"
                    + "--> Insert/Remove sequence (I...Insert; R...Remove; operation in brackets \"()\" was unsuccessful because of duplicate or not existing node; the very last operation caused the error):\n\t"
                    + "    ---------------------------------------------------------------------------------------------\n\t"
                    + OperationSequence + "\n\t"
                    + "\nTree before remove:\n\t" + sbTreeBefore.toString() + "\n\n\tTree after remove:" + sbTreeAfter.toString() + "\n\t";
            assertTrue(check, "Integrity" + strError);
            assertTrue(tree.getTreeHeight() <= (1.44 * (Math.log(tree.getSize() + 2) / Math.log(2)) - 0.328), "Height" + strError);
        }

        System.out.println("AVL integrity check successful  (number of operations processed: " + num_of_operations + ")\n\t"
                + "--> Insert/Remove sequence (I...Insert; R...Remove; operation in brackets \"()\" was unsuccessful because of duplicate or not existing node):\n\t"
//				+ "--------------------------------------------------------------------------------------------------------\n\t"
                + OperationSequence + "\n\t"
                + "\n\tFinal tree dump:" + display());
    }