@Override
    public Position position(int major, int minor) {
        return new Pos(major, minor);
    }
@Test
    public void testNegativeOffsetWithForwardBias() {
        Position pos = navigator.position(4, 10);
        pos = pos.offsetBy(-10, Forward);
        assertEquals(4, pos.getMajor());
        assertEquals(0, pos.getMinor());
    }