verify Plugin equals method (#12575)

pinot-spi/pom.xml

@@ -139,6 +139,11 @@
       <artifactId>testng</artifactId>
       <scope>test</scope>
     </dependency>
+    <dependency>
+      <groupId>nl.jqno.equalsverifier</groupId>
+      <artifactId>equalsverifier</artifactId>
+      <scope>test</scope>
+    </dependency>
     <dependency>
       <groupId>org.reflections</groupId>
       <artifactId>reflections</artifactId>

pinot-spi/src/main/java/org/apache/pinot/spi/plugin/Plugin.java

@@ -21,9 +21,9 @@
 import java.util.Objects;
 
 
-public class Plugin {
+public final class Plugin {
 
-  String _name;
+  final String _name;
 
   public Plugin(String name) {
     _name = name;

pinot-spi/src/test/java/org/apache/pinot/spi/plugin/PluginTest.java

@@ -0,0 +1,31 @@
+/**
+ * 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.pinot.spi.plugin;
+
+import nl.jqno.equalsverifier.EqualsVerifier;
+import org.testng.annotations.Test;
+
+
+public class PluginTest {
+
+  @Test
+  public void equalsVerifier() {
+    EqualsVerifier.forClass(Plugin.class).verify();
+  }
+}