### Question:
ClusterHandler { public ClusterHandler(InvokerRepository<T> repository) { this.repository = repository; this.serviceInterface = repository.getServiceInterface(); } ClusterHandler(InvokerRepository<T> repository); Class<T> getInterface(); RpcResult handle(RpcInvocation invocation); void destroy(); InvokerRepository<T> getRepository();  }### Answer:
@Test public void testClusterHandler() { InvokerRepository repository = MockUtil.getInvokerRepository(); MockCluster.MockClusterHandler clusterHandler = new MockCluster.MockClusterHandler(repository); try { clusterHandler.handle(MockUtil.getRpcInvocation()); } catch (Throwable e) { Assert.fail(); } repository = MockUtil.getEmptyInvokerRepository(); clusterHandler = new MockCluster.MockClusterHandler(repository); try { clusterHandler.handle(MockUtil.getRpcInvocation()); } catch (Throwable e) { Assert.assertTrue(e instanceof RegistryException); Assert.assertTrue(e.getMessage().contains("Provider list is empty")); } }