[SPARK-29158][SQL][FOLLOW-UP] Create an actual test case under src/test and minor documentation correction

core/src/main/scala/org/apache/spark/util/SerializableConfiguration.scala

@@ -23,8 +23,9 @@ import org.apache.hadoop.conf.Configuration
 import org.apache.spark.annotation.{DeveloperApi, Unstable}
 
 /**
- * Helper wrapper to serialize a Hadoop configuration. Intended for use when implementing
- * DataSourceV2 readers & writers which depend on the Hadoop configuration from the driver node.
+ * Hadoop configuration but serializable. Use `value` to access the Hadoop configuration.
+ *
+ * @param value Hadoop configuration
  */
 @DeveloperApi @Unstable
 class SerializableConfiguration(@transient var value: Configuration) extends Serializable {

core/src/test/java/org/apache/spark/util/SerializableConfigurationSuite.java

@@ -0,0 +1,55 @@
+/*
+ * 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.spark.util;
+
+import java.util.Arrays;
+
+import org.apache.hadoop.conf.Configuration;
+import org.junit.After;
+import org.junit.Before;
+import org.junit.Test;
+
+import org.apache.spark.api.java.JavaRDD;
+import org.apache.spark.api.java.JavaSparkContext;
+
+import static org.junit.Assert.assertEquals;
+
+
+public class SerializableConfigurationSuite {
+  private transient JavaSparkContext sc;
+
+  @Before
+  public void setUp() {
+    sc = new JavaSparkContext("local", "SerializableConfigurationSuite");
+  }
+
+  @After
+  public void tearDown() {
+    sc.stop();
+    sc = null;
+  }
+
+  @Test
+  public void testSerializableConfiguration() {
+    JavaRDD<Integer> rdd = sc.parallelize(Arrays.asList(1, 2, 3, 4), 2);
+    Configuration hadoopConfiguration = new Configuration(false);
+    hadoopConfiguration.set("test.property", "value");
+    SerializableConfiguration scs = new SerializableConfiguration(hadoopConfiguration);
+    SerializableConfiguration actual = rdd.map(val -> scs).collect().get(0);
+    assertEquals(actual.value().get("test.property"), "value");
+  }
+}