@Test
    public void testRightNested(){
        String input = "((x * x) * 2)";
        String var = "x";
        String expected = "(((x * x) * 0) + (2 * ((x * 1) + (x * 1))))";
        Differentiator diff = new Differentiator();
        assertEquals(expected, diff.evaluate(input, var));
    }