@Override
    public Position position(int major, int minor) {
        return new Pos(major, minor);
    }
@Test
    public void testNegativeOffsetWithBackwardBias() {
        Position pos = navigator.position(4, 10);
        pos = pos.offsetBy(-10, Backward);
        assertEquals(3, pos.getMajor());
        assertEquals(10, pos.getMinor());
    }