public RegionId region() {
        String r = get(REGION, null);
        return r == null ? null : regionId(r);
    }
@Test
    public void setRegion() {
        loadLayout(L1);
        assertEquals("not region-1", R1, cfg.region());
        cfg.region(NEW_REGION);
        assertEquals("not new region", NEW_REGION, cfg.region());
        cfg.region(null);
        assertNull("region not cleared", cfg.region());
    }