@Test
    public void testCalculateDistance() {
        mass = new Mass(1, 1);
        Mass other = new Mass(2, 1);
        assertEquals(1d, mass.calculateDistance(other), DELTA);

        other = new Mass(0, 1);
        assertEquals(1d, mass.calculateDistance(other), DELTA);

        other = new Mass(0, 0);
        assertEquals(Math.sqrt(2d), mass.calculateDistance(other), DELTA);
    }