### Question:
DBDeviceGroupManager extends DBManager<DeviceGroup> implements DeviceGroupManager { @Override public final Set<DeviceGroup> getDeviceGroupSet() throws DeviceGroupManagerException { LOGGER.debug("getting device group list"); try { final List<DeviceGroup> deviceGroupList = super.getList(DeviceGroup.class); return new HashSet<>(deviceGroupList); } catch (DBManagerException e) { throw new DeviceGroupManagerException(e); } } DBDeviceGroupManager(final SessionFactory factory); @Override final DeviceGroup saveDeviceGroup(final DeviceGroup deviceGroup); @Override final void updateDeviceGroup(final DeviceGroup deviceGroup); @Override final Set<DeviceGroup> getDeviceGroupSet(); @Override final DeviceGroup getDeviceGroup(final String name); @Override final Set<DeviceGroup> getGroupsAssignedToPolicy(final Policy policy); @Override final boolean deleteDeviceGroup(final String name); @Override final FilteredRecordsList<DeviceGroup> getOrderedDeviceGroupList(
            final String columnToOrder, final boolean ascending, final int firstResult,
            final int maxResults, final String search);  }### Answer:
@Test public void testGetDeviceGroupListEmptyList() { LOGGER.debug("testGetDeviceGroupListEmptyList test started"); final DeviceGroupManager mgr = new DBDeviceGroupManager(sessionFactory); final Set<DeviceGroup> deviceGroupSet = new HashSet<>(); final Set<DeviceGroup> dbDeviceGroupSet = mgr.getDeviceGroupSet(); Assert.assertEquals(deviceGroupSet, dbDeviceGroupSet); }