    @Test
    public void testNdgc() {

        double ndgc = (
                (0.80 + 0.00 / Math.log(2+1) + 0.95 / Math.log(4+1) + 0.91 / Math.log(7+1))
                        / (0.95 + 0.91 / Math.log(2+1) + 0.80 / Math.log(4+1) + 0.00 / Math.log(7+1)));
        assertEquals(ndgc, guess.getNDGC(), 0.001);
    }