[GitHub] [dubbo] pinxiong commented on a change in pull request #8525: service discovery registry process test

[GitBox <gi...@apache.org>]

pinxiong commented on a change in pull request #8525:
URL: https://github.com/apache/dubbo/pull/8525#discussion_r690009572



##########
File path: dubbo-config/dubbo-config-api/src/test/java/org/apache/dubbo/integration/single/serviceDiscoveryRegistry/SingleRegistryCenterServiceDiscoveryRegistryIntegrationTest.java
##########
@@ -0,0 +1,206 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements.  See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The ASF licenses this file to You under the Apache License, Version 2.0
+ * (the "License"); you may not use this file except in compliance with
+ * the License.  You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package org.apache.dubbo.integration.single.serviceDiscoveryRegistry;
+
+import com.alibaba.nacos.common.utils.MapUtil;
+import org.apache.dubbo.common.constants.CommonConstants;
+import org.apache.dubbo.common.extension.ExtensionLoader;
+import org.apache.dubbo.common.utils.CollectionUtils;
+import org.apache.dubbo.config.*;

Review comment:
       See above first.
   
   Also, you need to remove import*

##########
File path: dubbo-config/dubbo-config-api/src/test/java/org/apache/dubbo/integration/single/serviceDiscoveryRegistry/SingleRegistryCenterServiceDiscoveryRegistryIntegrationTest.java
##########
@@ -0,0 +1,206 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements.  See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The ASF licenses this file to You under the Apache License, Version 2.0
+ * (the "License"); you may not use this file except in compliance with
+ * the License.  You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package org.apache.dubbo.integration.single.serviceDiscoveryRegistry;
+
+import com.alibaba.nacos.common.utils.MapUtil;
+import org.apache.dubbo.common.constants.CommonConstants;
+import org.apache.dubbo.common.extension.ExtensionLoader;
+import org.apache.dubbo.common.utils.CollectionUtils;
+import org.apache.dubbo.config.*;
+import org.apache.dubbo.config.bootstrap.DubboBootstrap;
+import org.apache.dubbo.integration.IntegrationTest;
+import org.apache.dubbo.integration.single.injvm.SingleRegistryCenterInjvmService;
+import org.apache.dubbo.integration.single.injvm.SingleRegistryCenterInjvmServiceImpl;
+import org.apache.dubbo.integration.ServiceDiscoveryRegistryListener;
+import org.apache.dubbo.metadata.MetadataInfo;
+import org.apache.dubbo.metadata.WritableMetadataService;
+import org.apache.dubbo.registry.RegistryServiceListener;
+import org.apache.dubbo.registrycenter.DefaultMultipleRegistryCenter;
+import org.apache.dubbo.registrycenter.DefaultSingleRegistryCenter;
+import org.apache.dubbo.registrycenter.MultipleRegistryCenter;
+import org.apache.dubbo.registrycenter.SingleRegistryCenter;
+import org.apache.dubbo.rpc.ExporterListener;
+import org.apache.dubbo.rpc.Filter;
+import org.junit.jupiter.api.AfterEach;
+import org.junit.jupiter.api.Assertions;
+import org.junit.jupiter.api.BeforeEach;
+import org.junit.jupiter.api.Test;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
+import java.io.IOException;
+import java.util.Map;
+import java.util.Set;
+import java.util.SortedSet;
+
+import static org.apache.dubbo.rpc.Constants.SCOPE_LOCAL;
+
+/**
+ * The testcases are only for checking the process of saving metainfos for service-discovery-registry protocol.
+ */
+public class SingleRegistryCenterServiceDiscoveryRegistryIntegrationTest implements IntegrationTest {
+
+    private static final Logger logger = LoggerFactory.getLogger(SingleRegistryCenterServiceDiscoveryRegistryIntegrationTest.class);
+
+    /**
+     * Define the provider application name.
+     */
+    private static String PROVIDER_APPLICATION_NAME = "single-registry-center-provider-for-service-discovery-registry-protocol";
+
+    /**
+     * Define the protocol's name.
+     */
+    private static String PROTOCOL_NAME = CommonConstants.DUBBO;
+    /**
+     * Define the protocol's port.
+     */
+    private static int PROTOCOL_PORT = 20880;
+
+    /**
+     * The name for getting the specified instance, which is loaded using SPI.
+     */
+    private static String SPI_NAME = "singleConfigCenterServiceDiscoveryRegistry";
+    /**
+     * Define the {@link ServiceConfig} instance.
+     */
+    private ServiceConfig<SingleRegistryCenterInjvmService> serviceConfig;

Review comment:
       Define a new service

##########
File path: dubbo-config/dubbo-config-api/src/test/java/org/apache/dubbo/integration/single/serviceDiscoveryRegistry/SingleRegistryCenterServiceDiscoveryRegistryIntegrationTest.java
##########
@@ -0,0 +1,206 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements.  See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The ASF licenses this file to You under the Apache License, Version 2.0
+ * (the "License"); you may not use this file except in compliance with
+ * the License.  You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package org.apache.dubbo.integration.single.serviceDiscoveryRegistry;
+
+import com.alibaba.nacos.common.utils.MapUtil;
+import org.apache.dubbo.common.constants.CommonConstants;
+import org.apache.dubbo.common.extension.ExtensionLoader;
+import org.apache.dubbo.common.utils.CollectionUtils;
+import org.apache.dubbo.config.*;
+import org.apache.dubbo.config.bootstrap.DubboBootstrap;
+import org.apache.dubbo.integration.IntegrationTest;
+import org.apache.dubbo.integration.single.injvm.SingleRegistryCenterInjvmService;
+import org.apache.dubbo.integration.single.injvm.SingleRegistryCenterInjvmServiceImpl;
+import org.apache.dubbo.integration.ServiceDiscoveryRegistryListener;
+import org.apache.dubbo.metadata.MetadataInfo;
+import org.apache.dubbo.metadata.WritableMetadataService;
+import org.apache.dubbo.registry.RegistryServiceListener;
+import org.apache.dubbo.registrycenter.DefaultMultipleRegistryCenter;
+import org.apache.dubbo.registrycenter.DefaultSingleRegistryCenter;
+import org.apache.dubbo.registrycenter.MultipleRegistryCenter;
+import org.apache.dubbo.registrycenter.SingleRegistryCenter;
+import org.apache.dubbo.rpc.ExporterListener;
+import org.apache.dubbo.rpc.Filter;
+import org.junit.jupiter.api.AfterEach;
+import org.junit.jupiter.api.Assertions;
+import org.junit.jupiter.api.BeforeEach;
+import org.junit.jupiter.api.Test;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
+import java.io.IOException;
+import java.util.Map;
+import java.util.Set;
+import java.util.SortedSet;
+
+import static org.apache.dubbo.rpc.Constants.SCOPE_LOCAL;
+
+/**
+ * The testcases are only for checking the process of saving metainfos for service-discovery-registry protocol.
+ */
+public class SingleRegistryCenterServiceDiscoveryRegistryIntegrationTest implements IntegrationTest {
+
+    private static final Logger logger = LoggerFactory.getLogger(SingleRegistryCenterServiceDiscoveryRegistryIntegrationTest.class);
+
+    /**
+     * Define the provider application name.
+     */
+    private static String PROVIDER_APPLICATION_NAME = "single-registry-center-provider-for-service-discovery-registry-protocol";
+
+    /**
+     * Define the protocol's name.
+     */
+    private static String PROTOCOL_NAME = CommonConstants.DUBBO;
+    /**
+     * Define the protocol's port.
+     */
+    private static int PROTOCOL_PORT = 20880;
+
+    /**
+     * The name for getting the specified instance, which is loaded using SPI.
+     */
+    private static String SPI_NAME = "singleConfigCenterServiceDiscoveryRegistry";
+    /**
+     * Define the {@link ServiceConfig} instance.
+     */
+    private ServiceConfig<SingleRegistryCenterInjvmService> serviceConfig;
+
+    /**
+     * The listener to mark is Called
+     */
+    private ServiceDiscoveryRegistryListener registryServiceListener;
+
+    /**
+     * the service to write meta info locally
+     */
+    private WritableMetadataService writableMetadataService;
+
+    /**
+     * Default a registry center.
+     */
+    private SingleRegistryCenter registryCenter;
+
+    @BeforeEach
+    public void setUp() throws Exception {
+        logger.info(getClass().getSimpleName() + " testcase is beginning...");
+        DubboBootstrap.reset();
+
+        //start all zookeeper services only once
+        registryCenter = new DefaultSingleRegistryCenter();
+        registryCenter.startup();
+
+        // initialize service config
+        serviceConfig = new ServiceConfig<SingleRegistryCenterInjvmService>();
+        serviceConfig.setInterface(SingleRegistryCenterInjvmService.class);
+        serviceConfig.setRef(new SingleRegistryCenterInjvmServiceImpl());
+        serviceConfig.setAsync(false);
+//        serviceConfig.setScope(SCOPE_LOCAL);
+
+        // initailize bootstrap
+        DubboBootstrap.getInstance().registry(registryCenter.getRegistryConfig());
+
+        // initailize bootstrap
+        DubboBootstrap.getInstance()
+            .application(new ApplicationConfig(PROVIDER_APPLICATION_NAME))
+            .protocol(new ProtocolConfig(PROTOCOL_NAME, PROTOCOL_PORT))
+            .service(serviceConfig);
+
+        writableMetadataService = WritableMetadataService.getDefaultExtension();
+    }
+
+    private void beforeServiceDiscoveryRegistry() {
+        // ---------------initialize--------------- //
+        registryServiceListener = (ServiceDiscoveryRegistryListener) ExtensionLoader.getExtensionLoader(RegistryServiceListener.class).getExtension(SPI_NAME);
+
+        // ---------------checkpoints--------------- //
+        // registryServiceListener onRegister is not called
+        Assertions.assertFalse(registryServiceListener.isRegisterHasCalled());
+        // registryServiceListener onSubscribe is not called
+        Assertions.assertFalse(registryServiceListener.isSubscribeHasCalled());
+        // exportedServiceURLs of InMemoryWritableMetadataService is empty
+        Assertions.assertTrue(CollectionUtils.isEmpty(writableMetadataService.getExportedURLs()));
+        // metadataInfos of InMemoryWritableMetadataService is empty
+        Assertions.assertTrue(MapUtil.isEmpty(writableMetadataService.getMetadataInfos()));
+        // serviceToAppsMapping of InMemoryWritableMetadataService is empty
+        Assertions.assertTrue(MapUtil.isEmpty(writableMetadataService.getCachedMapping()));
+    }
+
+    /**
+     * {@inheritDoc}
+     */
+    @Test
+    @Override
+    public void integrate() {
+        beforeServiceDiscoveryRegistry();
+        DubboBootstrap.getInstance().start();
+        afterServiceDiscoveryRegistry();
+    }
+
+    private void afterServiceDiscoveryRegistry() {
+        // ---------------initialize--------------- //
+        registryServiceListener = (ServiceDiscoveryRegistryListener) ExtensionLoader.getExtensionLoader(RegistryServiceListener.class).getExtension(SPI_NAME);
+
+        // ---------------checkpoints--------------- //
+        // registryServiceListener onRegister is called
+        Assertions.assertTrue(registryServiceListener.isRegisterHasCalled());
+        // registryServiceListener onSubscribe is called
+        Assertions.assertTrue(registryServiceListener.isSubscribeHasCalled());
+        // exportedServiceURLs of InMemoryWritableMetadataService is empty
+        Assertions.assertTrue(isCorrectForExportedURLs(writableMetadataService.getExportedURLs()));
+        // metadataInfos of InMemoryWritableMetadataService is empty
+        Assertions.assertTrue(isCorrectForMetadataInfos(writableMetadataService.getMetadataInfos()));
+        // serviceToAppsMapping of InMemoryWritableMetadataService is empty
+        Assertions.assertTrue(isCorrectForServiceToAppsMapping(writableMetadataService.getCachedMapping()));
+    }
+
+    private Boolean isCorrectForExportedURLs(SortedSet<String> exportedURLs) {
+        if(CollectionUtils.isEmpty(exportedURLs)) {
+            return false;
+        }
+        if(!exportedURLs.toString().contains(PROVIDER_APPLICATION_NAME) || !exportedURLs.toString().contains("SingleRegistryCenterInjvmService")) {
+            return false;
+        }
+        return true;
+    }
+
+    private Boolean isCorrectForMetadataInfos(Map<String, MetadataInfo> metadataInfos) {

Review comment:
       Add the necessary comments

##########
File path: dubbo-config/dubbo-config-api/src/test/java/org/apache/dubbo/integration/single/serviceDiscoveryRegistry/SingleRegistryCenterServiceDiscoveryRegistryIntegrationTest.java
##########
@@ -0,0 +1,206 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements.  See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The ASF licenses this file to You under the Apache License, Version 2.0
+ * (the "License"); you may not use this file except in compliance with
+ * the License.  You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package org.apache.dubbo.integration.single.serviceDiscoveryRegistry;
+
+import com.alibaba.nacos.common.utils.MapUtil;
+import org.apache.dubbo.common.constants.CommonConstants;
+import org.apache.dubbo.common.extension.ExtensionLoader;
+import org.apache.dubbo.common.utils.CollectionUtils;
+import org.apache.dubbo.config.*;
+import org.apache.dubbo.config.bootstrap.DubboBootstrap;
+import org.apache.dubbo.integration.IntegrationTest;
+import org.apache.dubbo.integration.single.injvm.SingleRegistryCenterInjvmService;
+import org.apache.dubbo.integration.single.injvm.SingleRegistryCenterInjvmServiceImpl;
+import org.apache.dubbo.integration.ServiceDiscoveryRegistryListener;
+import org.apache.dubbo.metadata.MetadataInfo;
+import org.apache.dubbo.metadata.WritableMetadataService;
+import org.apache.dubbo.registry.RegistryServiceListener;
+import org.apache.dubbo.registrycenter.DefaultMultipleRegistryCenter;
+import org.apache.dubbo.registrycenter.DefaultSingleRegistryCenter;
+import org.apache.dubbo.registrycenter.MultipleRegistryCenter;
+import org.apache.dubbo.registrycenter.SingleRegistryCenter;
+import org.apache.dubbo.rpc.ExporterListener;
+import org.apache.dubbo.rpc.Filter;
+import org.junit.jupiter.api.AfterEach;
+import org.junit.jupiter.api.Assertions;
+import org.junit.jupiter.api.BeforeEach;
+import org.junit.jupiter.api.Test;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
+import java.io.IOException;
+import java.util.Map;
+import java.util.Set;
+import java.util.SortedSet;
+
+import static org.apache.dubbo.rpc.Constants.SCOPE_LOCAL;
+
+/**
+ * The testcases are only for checking the process of saving metainfos for service-discovery-registry protocol.
+ */
+public class SingleRegistryCenterServiceDiscoveryRegistryIntegrationTest implements IntegrationTest {
+
+    private static final Logger logger = LoggerFactory.getLogger(SingleRegistryCenterServiceDiscoveryRegistryIntegrationTest.class);
+
+    /**
+     * Define the provider application name.
+     */
+    private static String PROVIDER_APPLICATION_NAME = "single-registry-center-provider-for-service-discovery-registry-protocol";
+
+    /**
+     * Define the protocol's name.
+     */
+    private static String PROTOCOL_NAME = CommonConstants.DUBBO;
+    /**
+     * Define the protocol's port.
+     */
+    private static int PROTOCOL_PORT = 20880;
+
+    /**
+     * The name for getting the specified instance, which is loaded using SPI.
+     */
+    private static String SPI_NAME = "singleConfigCenterServiceDiscoveryRegistry";

Review comment:
       It's `RegistryCenter` not `ConfigCenter`

##########
File path: dubbo-config/dubbo-config-api/src/test/java/org/apache/dubbo/integration/single/serviceDiscoveryRegistry/SingleRegistryCenterServiceDiscoveryRegistryIntegrationTest.java
##########
@@ -0,0 +1,206 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements.  See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The ASF licenses this file to You under the Apache License, Version 2.0
+ * (the "License"); you may not use this file except in compliance with
+ * the License.  You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package org.apache.dubbo.integration.single.serviceDiscoveryRegistry;
+
+import com.alibaba.nacos.common.utils.MapUtil;
+import org.apache.dubbo.common.constants.CommonConstants;
+import org.apache.dubbo.common.extension.ExtensionLoader;
+import org.apache.dubbo.common.utils.CollectionUtils;
+import org.apache.dubbo.config.*;
+import org.apache.dubbo.config.bootstrap.DubboBootstrap;
+import org.apache.dubbo.integration.IntegrationTest;
+import org.apache.dubbo.integration.single.injvm.SingleRegistryCenterInjvmService;
+import org.apache.dubbo.integration.single.injvm.SingleRegistryCenterInjvmServiceImpl;
+import org.apache.dubbo.integration.ServiceDiscoveryRegistryListener;
+import org.apache.dubbo.metadata.MetadataInfo;
+import org.apache.dubbo.metadata.WritableMetadataService;
+import org.apache.dubbo.registry.RegistryServiceListener;
+import org.apache.dubbo.registrycenter.DefaultMultipleRegistryCenter;
+import org.apache.dubbo.registrycenter.DefaultSingleRegistryCenter;
+import org.apache.dubbo.registrycenter.MultipleRegistryCenter;
+import org.apache.dubbo.registrycenter.SingleRegistryCenter;
+import org.apache.dubbo.rpc.ExporterListener;
+import org.apache.dubbo.rpc.Filter;
+import org.junit.jupiter.api.AfterEach;
+import org.junit.jupiter.api.Assertions;
+import org.junit.jupiter.api.BeforeEach;
+import org.junit.jupiter.api.Test;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
+import java.io.IOException;
+import java.util.Map;
+import java.util.Set;
+import java.util.SortedSet;
+
+import static org.apache.dubbo.rpc.Constants.SCOPE_LOCAL;
+
+/**
+ * The testcases are only for checking the process of saving metainfos for service-discovery-registry protocol.
+ */
+public class SingleRegistryCenterServiceDiscoveryRegistryIntegrationTest implements IntegrationTest {
+
+    private static final Logger logger = LoggerFactory.getLogger(SingleRegistryCenterServiceDiscoveryRegistryIntegrationTest.class);
+
+    /**
+     * Define the provider application name.
+     */
+    private static String PROVIDER_APPLICATION_NAME = "single-registry-center-provider-for-service-discovery-registry-protocol";
+
+    /**
+     * Define the protocol's name.
+     */
+    private static String PROTOCOL_NAME = CommonConstants.DUBBO;
+    /**
+     * Define the protocol's port.
+     */
+    private static int PROTOCOL_PORT = 20880;
+
+    /**
+     * The name for getting the specified instance, which is loaded using SPI.
+     */
+    private static String SPI_NAME = "singleConfigCenterServiceDiscoveryRegistry";
+    /**
+     * Define the {@link ServiceConfig} instance.
+     */
+    private ServiceConfig<SingleRegistryCenterInjvmService> serviceConfig;
+
+    /**
+     * The listener to mark is Called
+     */
+    private ServiceDiscoveryRegistryListener registryServiceListener;
+
+    /**
+     * the service to write meta info locally
+     */
+    private WritableMetadataService writableMetadataService;
+
+    /**
+     * Default a registry center.
+     */
+    private SingleRegistryCenter registryCenter;
+
+    @BeforeEach
+    public void setUp() throws Exception {
+        logger.info(getClass().getSimpleName() + " testcase is beginning...");
+        DubboBootstrap.reset();
+
+        //start all zookeeper services only once
+        registryCenter = new DefaultSingleRegistryCenter();
+        registryCenter.startup();
+
+        // initialize service config
+        serviceConfig = new ServiceConfig<SingleRegistryCenterInjvmService>();
+        serviceConfig.setInterface(SingleRegistryCenterInjvmService.class);
+        serviceConfig.setRef(new SingleRegistryCenterInjvmServiceImpl());
+        serviceConfig.setAsync(false);
+//        serviceConfig.setScope(SCOPE_LOCAL);
+
+        // initailize bootstrap
+        DubboBootstrap.getInstance().registry(registryCenter.getRegistryConfig());
+
+        // initailize bootstrap
+        DubboBootstrap.getInstance()
+            .application(new ApplicationConfig(PROVIDER_APPLICATION_NAME))
+            .protocol(new ProtocolConfig(PROTOCOL_NAME, PROTOCOL_PORT))
+            .service(serviceConfig);
+
+        writableMetadataService = WritableMetadataService.getDefaultExtension();
+    }
+
+    private void beforeServiceDiscoveryRegistry() {
+        // ---------------initialize--------------- //
+        registryServiceListener = (ServiceDiscoveryRegistryListener) ExtensionLoader.getExtensionLoader(RegistryServiceListener.class).getExtension(SPI_NAME);
+
+        // ---------------checkpoints--------------- //
+        // registryServiceListener onRegister is not called
+        Assertions.assertFalse(registryServiceListener.isRegisterHasCalled());
+        // registryServiceListener onSubscribe is not called
+        Assertions.assertFalse(registryServiceListener.isSubscribeHasCalled());
+        // exportedServiceURLs of InMemoryWritableMetadataService is empty
+        Assertions.assertTrue(CollectionUtils.isEmpty(writableMetadataService.getExportedURLs()));
+        // metadataInfos of InMemoryWritableMetadataService is empty
+        Assertions.assertTrue(MapUtil.isEmpty(writableMetadataService.getMetadataInfos()));
+        // serviceToAppsMapping of InMemoryWritableMetadataService is empty
+        Assertions.assertTrue(MapUtil.isEmpty(writableMetadataService.getCachedMapping()));
+    }
+
+    /**
+     * {@inheritDoc}
+     */
+    @Test
+    @Override
+    public void integrate() {
+        beforeServiceDiscoveryRegistry();
+        DubboBootstrap.getInstance().start();
+        afterServiceDiscoveryRegistry();
+    }
+
+    private void afterServiceDiscoveryRegistry() {
+        // ---------------initialize--------------- //
+        registryServiceListener = (ServiceDiscoveryRegistryListener) ExtensionLoader.getExtensionLoader(RegistryServiceListener.class).getExtension(SPI_NAME);

Review comment:
       Why is this method called twice

##########
File path: dubbo-config/dubbo-config-api/src/test/java/org/apache/dubbo/integration/single/serviceDiscoveryRegistry/SingleRegistryCenterServiceDiscoveryRegistryIntegrationTest.java
##########
@@ -0,0 +1,206 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements.  See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The ASF licenses this file to You under the Apache License, Version 2.0
+ * (the "License"); you may not use this file except in compliance with
+ * the License.  You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package org.apache.dubbo.integration.single.serviceDiscoveryRegistry;
+
+import com.alibaba.nacos.common.utils.MapUtil;
+import org.apache.dubbo.common.constants.CommonConstants;
+import org.apache.dubbo.common.extension.ExtensionLoader;
+import org.apache.dubbo.common.utils.CollectionUtils;
+import org.apache.dubbo.config.*;
+import org.apache.dubbo.config.bootstrap.DubboBootstrap;
+import org.apache.dubbo.integration.IntegrationTest;
+import org.apache.dubbo.integration.single.injvm.SingleRegistryCenterInjvmService;
+import org.apache.dubbo.integration.single.injvm.SingleRegistryCenterInjvmServiceImpl;
+import org.apache.dubbo.integration.ServiceDiscoveryRegistryListener;
+import org.apache.dubbo.metadata.MetadataInfo;
+import org.apache.dubbo.metadata.WritableMetadataService;
+import org.apache.dubbo.registry.RegistryServiceListener;
+import org.apache.dubbo.registrycenter.DefaultMultipleRegistryCenter;
+import org.apache.dubbo.registrycenter.DefaultSingleRegistryCenter;
+import org.apache.dubbo.registrycenter.MultipleRegistryCenter;
+import org.apache.dubbo.registrycenter.SingleRegistryCenter;
+import org.apache.dubbo.rpc.ExporterListener;
+import org.apache.dubbo.rpc.Filter;
+import org.junit.jupiter.api.AfterEach;
+import org.junit.jupiter.api.Assertions;
+import org.junit.jupiter.api.BeforeEach;
+import org.junit.jupiter.api.Test;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
+import java.io.IOException;
+import java.util.Map;
+import java.util.Set;
+import java.util.SortedSet;
+
+import static org.apache.dubbo.rpc.Constants.SCOPE_LOCAL;
+
+/**
+ * The testcases are only for checking the process of saving metainfos for service-discovery-registry protocol.
+ */
+public class SingleRegistryCenterServiceDiscoveryRegistryIntegrationTest implements IntegrationTest {
+
+    private static final Logger logger = LoggerFactory.getLogger(SingleRegistryCenterServiceDiscoveryRegistryIntegrationTest.class);
+
+    /**
+     * Define the provider application name.
+     */
+    private static String PROVIDER_APPLICATION_NAME = "single-registry-center-provider-for-service-discovery-registry-protocol";
+
+    /**
+     * Define the protocol's name.
+     */
+    private static String PROTOCOL_NAME = CommonConstants.DUBBO;
+    /**
+     * Define the protocol's port.
+     */
+    private static int PROTOCOL_PORT = 20880;
+
+    /**
+     * The name for getting the specified instance, which is loaded using SPI.
+     */
+    private static String SPI_NAME = "singleConfigCenterServiceDiscoveryRegistry";
+    /**
+     * Define the {@link ServiceConfig} instance.
+     */
+    private ServiceConfig<SingleRegistryCenterInjvmService> serviceConfig;
+
+    /**
+     * The listener to mark is Called
+     */
+    private ServiceDiscoveryRegistryListener registryServiceListener;
+
+    /**
+     * the service to write meta info locally
+     */
+    private WritableMetadataService writableMetadataService;
+
+    /**
+     * Default a registry center.
+     */
+    private SingleRegistryCenter registryCenter;
+
+    @BeforeEach
+    public void setUp() throws Exception {
+        logger.info(getClass().getSimpleName() + " testcase is beginning...");
+        DubboBootstrap.reset();
+
+        //start all zookeeper services only once
+        registryCenter = new DefaultSingleRegistryCenter();
+        registryCenter.startup();
+
+        // initialize service config
+        serviceConfig = new ServiceConfig<SingleRegistryCenterInjvmService>();
+        serviceConfig.setInterface(SingleRegistryCenterInjvmService.class);
+        serviceConfig.setRef(new SingleRegistryCenterInjvmServiceImpl());
+        serviceConfig.setAsync(false);
+//        serviceConfig.setScope(SCOPE_LOCAL);
+
+        // initailize bootstrap
+        DubboBootstrap.getInstance().registry(registryCenter.getRegistryConfig());
+
+        // initailize bootstrap
+        DubboBootstrap.getInstance()
+            .application(new ApplicationConfig(PROVIDER_APPLICATION_NAME))
+            .protocol(new ProtocolConfig(PROTOCOL_NAME, PROTOCOL_PORT))
+            .service(serviceConfig);
+
+        writableMetadataService = WritableMetadataService.getDefaultExtension();
+    }
+
+    private void beforeServiceDiscoveryRegistry() {
+        // ---------------initialize--------------- //
+        registryServiceListener = (ServiceDiscoveryRegistryListener) ExtensionLoader.getExtensionLoader(RegistryServiceListener.class).getExtension(SPI_NAME);
+
+        // ---------------checkpoints--------------- //
+        // registryServiceListener onRegister is not called
+        Assertions.assertFalse(registryServiceListener.isRegisterHasCalled());
+        // registryServiceListener onSubscribe is not called
+        Assertions.assertFalse(registryServiceListener.isSubscribeHasCalled());
+        // exportedServiceURLs of InMemoryWritableMetadataService is empty
+        Assertions.assertTrue(CollectionUtils.isEmpty(writableMetadataService.getExportedURLs()));
+        // metadataInfos of InMemoryWritableMetadataService is empty
+        Assertions.assertTrue(MapUtil.isEmpty(writableMetadataService.getMetadataInfos()));
+        // serviceToAppsMapping of InMemoryWritableMetadataService is empty
+        Assertions.assertTrue(MapUtil.isEmpty(writableMetadataService.getCachedMapping()));
+    }
+
+    /**
+     * {@inheritDoc}
+     */
+    @Test
+    @Override
+    public void integrate() {
+        beforeServiceDiscoveryRegistry();
+        DubboBootstrap.getInstance().start();
+        afterServiceDiscoveryRegistry();
+    }
+
+    private void afterServiceDiscoveryRegistry() {
+        // ---------------initialize--------------- //
+        registryServiceListener = (ServiceDiscoveryRegistryListener) ExtensionLoader.getExtensionLoader(RegistryServiceListener.class).getExtension(SPI_NAME);
+
+        // ---------------checkpoints--------------- //
+        // registryServiceListener onRegister is called
+        Assertions.assertTrue(registryServiceListener.isRegisterHasCalled());
+        // registryServiceListener onSubscribe is called
+        Assertions.assertTrue(registryServiceListener.isSubscribeHasCalled());
+        // exportedServiceURLs of InMemoryWritableMetadataService is empty
+        Assertions.assertTrue(isCorrectForExportedURLs(writableMetadataService.getExportedURLs()));
+        // metadataInfos of InMemoryWritableMetadataService is empty
+        Assertions.assertTrue(isCorrectForMetadataInfos(writableMetadataService.getMetadataInfos()));
+        // serviceToAppsMapping of InMemoryWritableMetadataService is empty
+        Assertions.assertTrue(isCorrectForServiceToAppsMapping(writableMetadataService.getCachedMapping()));
+    }
+
+    private Boolean isCorrectForExportedURLs(SortedSet<String> exportedURLs) {
+        if(CollectionUtils.isEmpty(exportedURLs)) {
+            return false;
+        }
+        if(!exportedURLs.toString().contains(PROVIDER_APPLICATION_NAME) || !exportedURLs.toString().contains("SingleRegistryCenterInjvmService")) {
+            return false;
+        }
+        return true;
+    }
+
+    private Boolean isCorrectForMetadataInfos(Map<String, MetadataInfo> metadataInfos) {
+        if(MapUtil.isEmpty(metadataInfos)) {
+            return false;
+        }
+        if(!metadataInfos.toString().contains(PROVIDER_APPLICATION_NAME) || !metadataInfos.toString().contains("SingleRegistryCenterInjvmService")) {
+            return false;
+        }
+        return true;
+    }
+
+    private Boolean isCorrectForServiceToAppsMapping(Map<String, Set<String>> serviceToAppsMapping) {

Review comment:
       It's unnecessary

##########
File path: dubbo-config/dubbo-config-api/src/test/java/org/apache/dubbo/integration/single/serviceDiscoveryRegistry/SingleRegistryCenterServiceDiscoveryRegistryIntegrationTest.java
##########
@@ -0,0 +1,206 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements.  See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The ASF licenses this file to You under the Apache License, Version 2.0
+ * (the "License"); you may not use this file except in compliance with
+ * the License.  You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package org.apache.dubbo.integration.single.serviceDiscoveryRegistry;
+
+import com.alibaba.nacos.common.utils.MapUtil;
+import org.apache.dubbo.common.constants.CommonConstants;
+import org.apache.dubbo.common.extension.ExtensionLoader;
+import org.apache.dubbo.common.utils.CollectionUtils;
+import org.apache.dubbo.config.*;
+import org.apache.dubbo.config.bootstrap.DubboBootstrap;
+import org.apache.dubbo.integration.IntegrationTest;
+import org.apache.dubbo.integration.single.injvm.SingleRegistryCenterInjvmService;
+import org.apache.dubbo.integration.single.injvm.SingleRegistryCenterInjvmServiceImpl;
+import org.apache.dubbo.integration.ServiceDiscoveryRegistryListener;
+import org.apache.dubbo.metadata.MetadataInfo;
+import org.apache.dubbo.metadata.WritableMetadataService;
+import org.apache.dubbo.registry.RegistryServiceListener;
+import org.apache.dubbo.registrycenter.DefaultMultipleRegistryCenter;
+import org.apache.dubbo.registrycenter.DefaultSingleRegistryCenter;
+import org.apache.dubbo.registrycenter.MultipleRegistryCenter;
+import org.apache.dubbo.registrycenter.SingleRegistryCenter;
+import org.apache.dubbo.rpc.ExporterListener;
+import org.apache.dubbo.rpc.Filter;
+import org.junit.jupiter.api.AfterEach;
+import org.junit.jupiter.api.Assertions;
+import org.junit.jupiter.api.BeforeEach;
+import org.junit.jupiter.api.Test;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
+import java.io.IOException;
+import java.util.Map;
+import java.util.Set;
+import java.util.SortedSet;
+
+import static org.apache.dubbo.rpc.Constants.SCOPE_LOCAL;
+
+/**
+ * The testcases are only for checking the process of saving metainfos for service-discovery-registry protocol.
+ */
+public class SingleRegistryCenterServiceDiscoveryRegistryIntegrationTest implements IntegrationTest {
+
+    private static final Logger logger = LoggerFactory.getLogger(SingleRegistryCenterServiceDiscoveryRegistryIntegrationTest.class);
+
+    /**
+     * Define the provider application name.
+     */
+    private static String PROVIDER_APPLICATION_NAME = "single-registry-center-provider-for-service-discovery-registry-protocol";
+
+    /**
+     * Define the protocol's name.
+     */
+    private static String PROTOCOL_NAME = CommonConstants.DUBBO;
+    /**
+     * Define the protocol's port.
+     */
+    private static int PROTOCOL_PORT = 20880;
+
+    /**
+     * The name for getting the specified instance, which is loaded using SPI.
+     */
+    private static String SPI_NAME = "singleConfigCenterServiceDiscoveryRegistry";
+    /**
+     * Define the {@link ServiceConfig} instance.
+     */
+    private ServiceConfig<SingleRegistryCenterInjvmService> serviceConfig;
+
+    /**
+     * The listener to mark is Called
+     */
+    private ServiceDiscoveryRegistryListener registryServiceListener;
+
+    /**
+     * the service to write meta info locally
+     */
+    private WritableMetadataService writableMetadataService;
+
+    /**
+     * Default a registry center.
+     */
+    private SingleRegistryCenter registryCenter;
+
+    @BeforeEach
+    public void setUp() throws Exception {
+        logger.info(getClass().getSimpleName() + " testcase is beginning...");
+        DubboBootstrap.reset();
+
+        //start all zookeeper services only once
+        registryCenter = new DefaultSingleRegistryCenter();
+        registryCenter.startup();
+
+        // initialize service config
+        serviceConfig = new ServiceConfig<SingleRegistryCenterInjvmService>();
+        serviceConfig.setInterface(SingleRegistryCenterInjvmService.class);
+        serviceConfig.setRef(new SingleRegistryCenterInjvmServiceImpl());
+        serviceConfig.setAsync(false);
+//        serviceConfig.setScope(SCOPE_LOCAL);
+
+        // initailize bootstrap
+        DubboBootstrap.getInstance().registry(registryCenter.getRegistryConfig());
+
+        // initailize bootstrap
+        DubboBootstrap.getInstance()
+            .application(new ApplicationConfig(PROVIDER_APPLICATION_NAME))
+            .protocol(new ProtocolConfig(PROTOCOL_NAME, PROTOCOL_PORT))
+            .service(serviceConfig);
+
+        writableMetadataService = WritableMetadataService.getDefaultExtension();
+    }
+
+    private void beforeServiceDiscoveryRegistry() {
+        // ---------------initialize--------------- //
+        registryServiceListener = (ServiceDiscoveryRegistryListener) ExtensionLoader.getExtensionLoader(RegistryServiceListener.class).getExtension(SPI_NAME);
+
+        // ---------------checkpoints--------------- //
+        // registryServiceListener onRegister is not called
+        Assertions.assertFalse(registryServiceListener.isRegisterHasCalled());
+        // registryServiceListener onSubscribe is not called
+        Assertions.assertFalse(registryServiceListener.isSubscribeHasCalled());
+        // exportedServiceURLs of InMemoryWritableMetadataService is empty
+        Assertions.assertTrue(CollectionUtils.isEmpty(writableMetadataService.getExportedURLs()));
+        // metadataInfos of InMemoryWritableMetadataService is empty
+        Assertions.assertTrue(MapUtil.isEmpty(writableMetadataService.getMetadataInfos()));
+        // serviceToAppsMapping of InMemoryWritableMetadataService is empty
+        Assertions.assertTrue(MapUtil.isEmpty(writableMetadataService.getCachedMapping()));
+    }
+
+    /**
+     * {@inheritDoc}
+     */
+    @Test
+    @Override
+    public void integrate() {
+        beforeServiceDiscoveryRegistry();
+        DubboBootstrap.getInstance().start();
+        afterServiceDiscoveryRegistry();
+    }
+
+    private void afterServiceDiscoveryRegistry() {
+        // ---------------initialize--------------- //
+        registryServiceListener = (ServiceDiscoveryRegistryListener) ExtensionLoader.getExtensionLoader(RegistryServiceListener.class).getExtension(SPI_NAME);
+
+        // ---------------checkpoints--------------- //
+        // registryServiceListener onRegister is called
+        Assertions.assertTrue(registryServiceListener.isRegisterHasCalled());
+        // registryServiceListener onSubscribe is called
+        Assertions.assertTrue(registryServiceListener.isSubscribeHasCalled());
+        // exportedServiceURLs of InMemoryWritableMetadataService is empty
+        Assertions.assertTrue(isCorrectForExportedURLs(writableMetadataService.getExportedURLs()));
+        // metadataInfos of InMemoryWritableMetadataService is empty
+        Assertions.assertTrue(isCorrectForMetadataInfos(writableMetadataService.getMetadataInfos()));
+        // serviceToAppsMapping of InMemoryWritableMetadataService is empty
+        Assertions.assertTrue(isCorrectForServiceToAppsMapping(writableMetadataService.getCachedMapping()));
+    }
+
+    private Boolean isCorrectForExportedURLs(SortedSet<String> exportedURLs) {

Review comment:
       Add the necessary comments

##########
File path: dubbo-config/dubbo-config-api/src/test/java/org/apache/dubbo/integration/ServiceDiscoveryRegistryListener.java
##########
@@ -0,0 +1,95 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements.  See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The ASF licenses this file to You under the Apache License, Version 2.0
+ * (the "License"); you may not use this file except in compliance with
+ * the License.  You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package org.apache.dubbo.integration;
+
+import org.apache.dubbo.common.URL;
+import org.apache.dubbo.common.constants.CommonConstants;
+import org.apache.dubbo.common.extension.Activate;
+import org.apache.dubbo.registry.Registry;
+import org.apache.dubbo.registry.RegistryServiceListener;
+
+@Activate(group = CommonConstants.PROVIDER, order = 1000)
+public class ServiceDiscoveryRegistryListener implements RegistryServiceListener {

Review comment:
       You'd better create a new package named `servicediscoveryregistry` and move all created files into it. Also, all created class should keep the same style, including but not limited to class name, field name etc.

##########
File path: dubbo-config/dubbo-config-api/src/test/java/org/apache/dubbo/integration/single/serviceDiscoveryRegistry/SingleRegistryCenterServiceDiscoveryRegistryIntegrationTest.java
##########
@@ -0,0 +1,206 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements.  See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The ASF licenses this file to You under the Apache License, Version 2.0
+ * (the "License"); you may not use this file except in compliance with
+ * the License.  You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package org.apache.dubbo.integration.single.serviceDiscoveryRegistry;
+
+import com.alibaba.nacos.common.utils.MapUtil;
+import org.apache.dubbo.common.constants.CommonConstants;
+import org.apache.dubbo.common.extension.ExtensionLoader;
+import org.apache.dubbo.common.utils.CollectionUtils;
+import org.apache.dubbo.config.*;
+import org.apache.dubbo.config.bootstrap.DubboBootstrap;
+import org.apache.dubbo.integration.IntegrationTest;
+import org.apache.dubbo.integration.single.injvm.SingleRegistryCenterInjvmService;
+import org.apache.dubbo.integration.single.injvm.SingleRegistryCenterInjvmServiceImpl;
+import org.apache.dubbo.integration.ServiceDiscoveryRegistryListener;
+import org.apache.dubbo.metadata.MetadataInfo;
+import org.apache.dubbo.metadata.WritableMetadataService;
+import org.apache.dubbo.registry.RegistryServiceListener;
+import org.apache.dubbo.registrycenter.DefaultMultipleRegistryCenter;
+import org.apache.dubbo.registrycenter.DefaultSingleRegistryCenter;
+import org.apache.dubbo.registrycenter.MultipleRegistryCenter;
+import org.apache.dubbo.registrycenter.SingleRegistryCenter;
+import org.apache.dubbo.rpc.ExporterListener;
+import org.apache.dubbo.rpc.Filter;
+import org.junit.jupiter.api.AfterEach;
+import org.junit.jupiter.api.Assertions;
+import org.junit.jupiter.api.BeforeEach;
+import org.junit.jupiter.api.Test;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
+import java.io.IOException;
+import java.util.Map;
+import java.util.Set;
+import java.util.SortedSet;
+
+import static org.apache.dubbo.rpc.Constants.SCOPE_LOCAL;
+
+/**
+ * The testcases are only for checking the process of saving metainfos for service-discovery-registry protocol.
+ */
+public class SingleRegistryCenterServiceDiscoveryRegistryIntegrationTest implements IntegrationTest {
+
+    private static final Logger logger = LoggerFactory.getLogger(SingleRegistryCenterServiceDiscoveryRegistryIntegrationTest.class);
+
+    /**
+     * Define the provider application name.
+     */
+    private static String PROVIDER_APPLICATION_NAME = "single-registry-center-provider-for-service-discovery-registry-protocol";
+
+    /**
+     * Define the protocol's name.
+     */
+    private static String PROTOCOL_NAME = CommonConstants.DUBBO;
+    /**
+     * Define the protocol's port.
+     */
+    private static int PROTOCOL_PORT = 20880;
+
+    /**
+     * The name for getting the specified instance, which is loaded using SPI.
+     */
+    private static String SPI_NAME = "singleConfigCenterServiceDiscoveryRegistry";
+    /**
+     * Define the {@link ServiceConfig} instance.
+     */
+    private ServiceConfig<SingleRegistryCenterInjvmService> serviceConfig;
+
+    /**
+     * The listener to mark is Called
+     */
+    private ServiceDiscoveryRegistryListener registryServiceListener;
+
+    /**
+     * the service to write meta info locally
+     */
+    private WritableMetadataService writableMetadataService;
+
+    /**
+     * Default a registry center.
+     */
+    private SingleRegistryCenter registryCenter;
+
+    @BeforeEach
+    public void setUp() throws Exception {
+        logger.info(getClass().getSimpleName() + " testcase is beginning...");
+        DubboBootstrap.reset();
+
+        //start all zookeeper services only once
+        registryCenter = new DefaultSingleRegistryCenter();
+        registryCenter.startup();
+
+        // initialize service config
+        serviceConfig = new ServiceConfig<SingleRegistryCenterInjvmService>();
+        serviceConfig.setInterface(SingleRegistryCenterInjvmService.class);
+        serviceConfig.setRef(new SingleRegistryCenterInjvmServiceImpl());
+        serviceConfig.setAsync(false);
+//        serviceConfig.setScope(SCOPE_LOCAL);
+
+        // initailize bootstrap
+        DubboBootstrap.getInstance().registry(registryCenter.getRegistryConfig());
+
+        // initailize bootstrap
+        DubboBootstrap.getInstance()
+            .application(new ApplicationConfig(PROVIDER_APPLICATION_NAME))
+            .protocol(new ProtocolConfig(PROTOCOL_NAME, PROTOCOL_PORT))
+            .service(serviceConfig);
+
+        writableMetadataService = WritableMetadataService.getDefaultExtension();
+    }
+
+    private void beforeServiceDiscoveryRegistry() {
+        // ---------------initialize--------------- //
+        registryServiceListener = (ServiceDiscoveryRegistryListener) ExtensionLoader.getExtensionLoader(RegistryServiceListener.class).getExtension(SPI_NAME);
+
+        // ---------------checkpoints--------------- //
+        // registryServiceListener onRegister is not called
+        Assertions.assertFalse(registryServiceListener.isRegisterHasCalled());
+        // registryServiceListener onSubscribe is not called
+        Assertions.assertFalse(registryServiceListener.isSubscribeHasCalled());
+        // exportedServiceURLs of InMemoryWritableMetadataService is empty
+        Assertions.assertTrue(CollectionUtils.isEmpty(writableMetadataService.getExportedURLs()));
+        // metadataInfos of InMemoryWritableMetadataService is empty
+        Assertions.assertTrue(MapUtil.isEmpty(writableMetadataService.getMetadataInfos()));
+        // serviceToAppsMapping of InMemoryWritableMetadataService is empty
+        Assertions.assertTrue(MapUtil.isEmpty(writableMetadataService.getCachedMapping()));
+    }
+
+    /**
+     * {@inheritDoc}
+     */
+    @Test
+    @Override
+    public void integrate() {
+        beforeServiceDiscoveryRegistry();
+        DubboBootstrap.getInstance().start();
+        afterServiceDiscoveryRegistry();
+    }
+
+    private void afterServiceDiscoveryRegistry() {

Review comment:
       You'd better describe the idea of verification

##########
File path: dubbo-config/dubbo-config-api/src/test/java/org/apache/dubbo/integration/single/serviceDiscoveryRegistry/SingleRegistryCenterServiceDiscoveryRegistryIntegrationTest.java
##########
@@ -0,0 +1,206 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements.  See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The ASF licenses this file to You under the Apache License, Version 2.0
+ * (the "License"); you may not use this file except in compliance with
+ * the License.  You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package org.apache.dubbo.integration.single.serviceDiscoveryRegistry;
+
+import com.alibaba.nacos.common.utils.MapUtil;
+import org.apache.dubbo.common.constants.CommonConstants;
+import org.apache.dubbo.common.extension.ExtensionLoader;
+import org.apache.dubbo.common.utils.CollectionUtils;
+import org.apache.dubbo.config.*;
+import org.apache.dubbo.config.bootstrap.DubboBootstrap;
+import org.apache.dubbo.integration.IntegrationTest;
+import org.apache.dubbo.integration.single.injvm.SingleRegistryCenterInjvmService;
+import org.apache.dubbo.integration.single.injvm.SingleRegistryCenterInjvmServiceImpl;
+import org.apache.dubbo.integration.ServiceDiscoveryRegistryListener;
+import org.apache.dubbo.metadata.MetadataInfo;
+import org.apache.dubbo.metadata.WritableMetadataService;
+import org.apache.dubbo.registry.RegistryServiceListener;
+import org.apache.dubbo.registrycenter.DefaultMultipleRegistryCenter;
+import org.apache.dubbo.registrycenter.DefaultSingleRegistryCenter;
+import org.apache.dubbo.registrycenter.MultipleRegistryCenter;
+import org.apache.dubbo.registrycenter.SingleRegistryCenter;
+import org.apache.dubbo.rpc.ExporterListener;
+import org.apache.dubbo.rpc.Filter;
+import org.junit.jupiter.api.AfterEach;
+import org.junit.jupiter.api.Assertions;
+import org.junit.jupiter.api.BeforeEach;
+import org.junit.jupiter.api.Test;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
+import java.io.IOException;
+import java.util.Map;
+import java.util.Set;
+import java.util.SortedSet;
+
+import static org.apache.dubbo.rpc.Constants.SCOPE_LOCAL;
+
+/**
+ * The testcases are only for checking the process of saving metainfos for service-discovery-registry protocol.
+ */
+public class SingleRegistryCenterServiceDiscoveryRegistryIntegrationTest implements IntegrationTest {
+
+    private static final Logger logger = LoggerFactory.getLogger(SingleRegistryCenterServiceDiscoveryRegistryIntegrationTest.class);
+
+    /**
+     * Define the provider application name.
+     */
+    private static String PROVIDER_APPLICATION_NAME = "single-registry-center-provider-for-service-discovery-registry-protocol";
+
+    /**
+     * Define the protocol's name.
+     */
+    private static String PROTOCOL_NAME = CommonConstants.DUBBO;
+    /**
+     * Define the protocol's port.
+     */
+    private static int PROTOCOL_PORT = 20880;
+
+    /**
+     * The name for getting the specified instance, which is loaded using SPI.
+     */
+    private static String SPI_NAME = "singleConfigCenterServiceDiscoveryRegistry";
+    /**
+     * Define the {@link ServiceConfig} instance.
+     */
+    private ServiceConfig<SingleRegistryCenterInjvmService> serviceConfig;
+
+    /**
+     * The listener to mark is Called
+     */
+    private ServiceDiscoveryRegistryListener registryServiceListener;
+
+    /**
+     * the service to write meta info locally
+     */
+    private WritableMetadataService writableMetadataService;
+
+    /**
+     * Default a registry center.
+     */
+    private SingleRegistryCenter registryCenter;
+
+    @BeforeEach
+    public void setUp() throws Exception {
+        logger.info(getClass().getSimpleName() + " testcase is beginning...");
+        DubboBootstrap.reset();
+
+        //start all zookeeper services only once
+        registryCenter = new DefaultSingleRegistryCenter();
+        registryCenter.startup();
+
+        // initialize service config
+        serviceConfig = new ServiceConfig<SingleRegistryCenterInjvmService>();
+        serviceConfig.setInterface(SingleRegistryCenterInjvmService.class);
+        serviceConfig.setRef(new SingleRegistryCenterInjvmServiceImpl());
+        serviceConfig.setAsync(false);
+//        serviceConfig.setScope(SCOPE_LOCAL);
+
+        // initailize bootstrap
+        DubboBootstrap.getInstance().registry(registryCenter.getRegistryConfig());
+
+        // initailize bootstrap
+        DubboBootstrap.getInstance()
+            .application(new ApplicationConfig(PROVIDER_APPLICATION_NAME))
+            .protocol(new ProtocolConfig(PROTOCOL_NAME, PROTOCOL_PORT))
+            .service(serviceConfig);
+
+        writableMetadataService = WritableMetadataService.getDefaultExtension();
+    }
+
+    private void beforeServiceDiscoveryRegistry() {
+        // ---------------initialize--------------- //
+        registryServiceListener = (ServiceDiscoveryRegistryListener) ExtensionLoader.getExtensionLoader(RegistryServiceListener.class).getExtension(SPI_NAME);
+
+        // ---------------checkpoints--------------- //
+        // registryServiceListener onRegister is not called
+        Assertions.assertFalse(registryServiceListener.isRegisterHasCalled());
+        // registryServiceListener onSubscribe is not called
+        Assertions.assertFalse(registryServiceListener.isSubscribeHasCalled());
+        // exportedServiceURLs of InMemoryWritableMetadataService is empty
+        Assertions.assertTrue(CollectionUtils.isEmpty(writableMetadataService.getExportedURLs()));
+        // metadataInfos of InMemoryWritableMetadataService is empty
+        Assertions.assertTrue(MapUtil.isEmpty(writableMetadataService.getMetadataInfos()));
+        // serviceToAppsMapping of InMemoryWritableMetadataService is empty
+        Assertions.assertTrue(MapUtil.isEmpty(writableMetadataService.getCachedMapping()));
+    }
+
+    /**
+     * {@inheritDoc}
+     */
+    @Test
+    @Override
+    public void integrate() {
+        beforeServiceDiscoveryRegistry();
+        DubboBootstrap.getInstance().start();
+        afterServiceDiscoveryRegistry();
+    }
+
+    private void afterServiceDiscoveryRegistry() {
+        // ---------------initialize--------------- //
+        registryServiceListener = (ServiceDiscoveryRegistryListener) ExtensionLoader.getExtensionLoader(RegistryServiceListener.class).getExtension(SPI_NAME);
+
+        // ---------------checkpoints--------------- //
+        // registryServiceListener onRegister is called
+        Assertions.assertTrue(registryServiceListener.isRegisterHasCalled());
+        // registryServiceListener onSubscribe is called
+        Assertions.assertTrue(registryServiceListener.isSubscribeHasCalled());
+        // exportedServiceURLs of InMemoryWritableMetadataService is empty
+        Assertions.assertTrue(isCorrectForExportedURLs(writableMetadataService.getExportedURLs()));
+        // metadataInfos of InMemoryWritableMetadataService is empty
+        Assertions.assertTrue(isCorrectForMetadataInfos(writableMetadataService.getMetadataInfos()));
+        // serviceToAppsMapping of InMemoryWritableMetadataService is empty
+        Assertions.assertTrue(isCorrectForServiceToAppsMapping(writableMetadataService.getCachedMapping()));
+    }
+
+    private Boolean isCorrectForExportedURLs(SortedSet<String> exportedURLs) {
+        if(CollectionUtils.isEmpty(exportedURLs)) {
+            return false;
+        }
+        if(!exportedURLs.toString().contains(PROVIDER_APPLICATION_NAME) || !exportedURLs.toString().contains("SingleRegistryCenterInjvmService")) {
+            return false;
+        }
+        return true;
+    }
+
+    private Boolean isCorrectForMetadataInfos(Map<String, MetadataInfo> metadataInfos) {
+        if(MapUtil.isEmpty(metadataInfos)) {
+            return false;
+        }
+        if(!metadataInfos.toString().contains(PROVIDER_APPLICATION_NAME) || !metadataInfos.toString().contains("SingleRegistryCenterInjvmService")) {
+            return false;
+        }
+        return true;
+    }
+
+    private Boolean isCorrectForServiceToAppsMapping(Map<String, Set<String>> serviceToAppsMapping) {
+        return true;
+    }
+
+    @AfterEach
+    public void tearDown() throws IOException {
+        DubboBootstrap.reset();
+        PROVIDER_APPLICATION_NAME = null;
+        serviceConfig = null;
+        Assertions.assertTrue(registryServiceListener.isUnRegisterHasCalled());
+        Assertions.assertTrue(registryServiceListener.isUnSubscribeHasCalled());
+        logger.info(getClass().getSimpleName() + " testcase is ending...");
+        // destroy registry center
+        registryCenter.shutdown();
+        registryCenter = null;

Review comment:
       Release all defined private variables




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