[ISSUE apache#8413] Add some test cases for commom module

common/src/test/java/org/apache/rocketmq/common/BrokerConfigSingletonTest.java

@@ -0,0 +1,46 @@
+/*
+ * 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.rocketmq.common;
+
+import org.junit.Assert;
+import org.junit.Test;
+
+public class BrokerConfigSingletonTest {
+
+    /**
+     * Tests the behavior of getting the broker configuration when it has not been initialized.
+     * Expects an IllegalArgumentException to be thrown, ensuring that the configuration cannot be obtained without initialization.
+     */
+    @Test(expected = IllegalArgumentException.class)
+    public void getBrokerConfig_NullConfiguration_ThrowsException() {
+        BrokerConfigSingleton.getBrokerConfig();
+    }
+
+    /**
+     * Tests the behavior of setting the broker configuration after it has already been initialized.
+     * Expects an IllegalArgumentException to be thrown, ensuring that the configuration cannot be reset once set.
+     * Also asserts that the returned brokerConfig instance is the same as the one set, confirming the singleton property.
+     */
+    @Test(expected = IllegalArgumentException.class)
+    public void setBrokerConfig_AlreadyInitialized_ThrowsException() {
+        BrokerConfig config = new BrokerConfig();
+        BrokerConfigSingleton.setBrokerConfig(config);
+        Assert.assertSame("Expected brokerConfig instance is not returned", config, BrokerConfigSingleton.getBrokerConfig());
+        BrokerConfigSingleton.setBrokerConfig(config);
+    }
+
+}