code: @Test public void testExecute() throws Exception {
    ProviderModel providerModel=mock(ProviderModel.class);
    when(providerModel.getServiceName()).thenReturn("org.apache.dubbo.BarService");
    ApplicationModel.initProviderModel("org.apache.dubbo.BarService",providerModel);
    Invoker providerInvoker=mock(Invoker.class);
    URL registryUrl=mock(URL.class);
    when(registryUrl.toFullString()).thenReturn("test://localhost:8080");
    URL providerUrl=mock(URL.class);
    when(providerUrl.getServiceKey()).thenReturn("org.apache.dubbo.BarService");
    when(providerUrl.toFullString()).thenReturn("dubbo://localhost:8888/org.apache.dubbo.BarService");
    when(providerInvoker.getUrl()).thenReturn(providerUrl);
    ProviderConsumerRegTable.registerProvider(providerInvoker,registryUrl,providerUrl);
    for (  ProviderInvokerWrapper wrapper : getProviderInvoker("org.apache.dubbo.BarService")) {
      wrapper.setReg(true);
    }
    Registry registry=mock(Registry.class);
    TestRegistryFactory.registry=registry;
    Offline offline=new Offline();
    String output=offline.execute(mock(CommandContext.class),new String[]{"org.apache.dubbo.BarService"});
    assertThat(output,containsString("OK"));
    Mockito.verify(registry).unregister(providerUrl);
    for (  ProviderInvokerWrapper wrapper : getProviderInvoker("org.apache.dubbo.BarService")) {
      assertThat(wrapper.isReg(),is(false));
    }
    output=offline.execute(mock(CommandContext.class),new String[]{"org.apache.dubbo.FooService"});
    assertThat(output,containsString("service not found"));
  }
  