add unit testcase for propertiesProviders

dubbo-common/src/main/java/org/apache/dubbo/common/config/PropertiesConfiguration.java

@@ -34,8 +34,8 @@ public PropertiesConfiguration(String prefix, String id) {
         super(prefix, id);
 
         ExtensionLoader<OrderedPropertiesProvider> propertiesProviderExtensionLoader = ExtensionLoader.getExtensionLoader(OrderedPropertiesProvider.class);
-        Set<String> propertiesProviderNames = propertiesProviderExtensionLoader.getLoadedExtensions();
-        if (propertiesProviderNames == null) {
+        Set<String> propertiesProviderNames = propertiesProviderExtensionLoader.getSupportedExtensions();
+        if (propertiesProviderNames == null || propertiesProviderNames.isEmpty()) {
             return;
         }
         List<OrderedPropertiesProvider> orderedPropertiesProviders = new ArrayList<>();

dubbo-common/src/test/java/org/apache/dubbo/common/config/MockOrderedPropertiesProvider1.java

@@ -0,0 +1,33 @@
+/*
+ * 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.common.config;
+
+import java.util.Properties;
+
+public class MockOrderedPropertiesProvider1 implements OrderedPropertiesProvider {
+    @Override
+    public int priority() {
+        return 3;
+    }
+
+    @Override
+    public Properties initProperties() {
+        Properties properties = new Properties();
+        properties.put("testKey", "333");
+        return properties;
+    }
+}

dubbo-common/src/test/java/org/apache/dubbo/common/config/MockOrderedPropertiesProvider2.java

@@ -0,0 +1,33 @@
+/*
+ * 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.common.config;
+
+import java.util.Properties;
+
+public class MockOrderedPropertiesProvider2 implements OrderedPropertiesProvider {
+    @Override
+    public int priority() {
+        return 1;
+    }
+
+    @Override
+    public Properties initProperties() {
+        Properties properties = new Properties();
+        properties.put("testKey", "999");
+        return properties;
+    }
+}

dubbo-common/src/test/java/org/apache/dubbo/common/config/PropertiesConfigurationTest.java

@@ -0,0 +1,30 @@
+/*
+ * 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.common.config;
+
+import org.junit.Assert;
+import org.junit.Test;
+
+public class PropertiesConfigurationTest {
+
+    @Test
+    public void testOrderPropertiesProviders() {
+        PropertiesConfiguration configuration = new PropertiesConfiguration("test", null);
+        Assert.assertTrue(configuration.getInternalProperty("testKey").equals("999"));
+    }
+
+}

dubbo-common/src/test/resources/META-INF/dubbo/internal/org.apache.dubbo.common.config.OrderedPropertiesProvider

@@ -0,0 +1,2 @@
+mock1=org.apache.dubbo.common.config.MockOrderedPropertiesProvider1
+mock2=org.apache.dubbo.common.config.MockOrderedPropertiesProvider2