@Override
    public MastershipRole getRole(DeviceId deviceId) {
        checkNotNull(deviceId, DEVICE_NULL);
        // TODO hard coded to master for now.
        return MastershipRole.MASTER;
    }
@Test(expected = NullPointerException.class)
    public void testGetRoleByNullId() {
        manager.registerTenantId(TenantId.tenantId(tenantIdValue1));
        VirtualNetwork virtualNetwork = manager.createVirtualNetwork(TenantId.tenantId(tenantIdValue1));
        DeviceService deviceService = manager.get(virtualNetwork.id(), DeviceService.class);

        // test the getRole() method using a null device identifier
        deviceService.getRole(null);
    }