Add missing unit test

Signed-off-by: currantw <[email protected]>

opensearch/src/test/java/org/opensearch/sql/opensearch/data/value/OpenSearchExprIpValueTest.java

@@ -5,40 +5,44 @@
 
 package org.opensearch.sql.opensearch.data.value;
 
-import static org.junit.jupiter.api.Assertions.assertEquals;
-import static org.junit.jupiter.api.Assertions.assertNotNull;
-import static org.junit.jupiter.api.Assertions.assertTrue;
+import static org.junit.jupiter.api.Assertions.*;
 
 import org.junit.jupiter.api.Test;
 import org.opensearch.sql.opensearch.data.type.OpenSearchIpType;
 
 public class OpenSearchExprIpValueTest {
 
-  private OpenSearchExprIpValue ipValue = new OpenSearchExprIpValue("192.168.0.1");
+  private final String ipString = "192.168.0.1";
+  private final OpenSearchExprIpValue ipValue = new OpenSearchExprIpValue(ipString);
 
   @Test
-  void value() {
-    assertEquals("192.168.0.1", ipValue.value());
+  void testValue() {
+    assertEquals(ipString, ipValue.value());
   }
 
   @Test
-  void type() {
+  void testType() {
     assertEquals(OpenSearchIpType.of(), ipValue.type());
   }
 
   @Test
-  void compare() {
-    assertEquals(0, ipValue.compareTo(new OpenSearchExprIpValue("192.168.0.1")));
-    assertEquals(ipValue, new OpenSearchExprIpValue("192.168.0.1"));
+  void testCompare() {
+    assertEquals(0, ipValue.compareTo(new OpenSearchExprIpValue(ipString)));
+    assertEquals(ipValue, new OpenSearchExprIpValue(ipString));
   }
 
   @Test
-  void equal() {
-    assertTrue(ipValue.equal(new OpenSearchExprIpValue("192.168.0.1")));
+  void testEqual() {
+    assertTrue(ipValue.equal(new OpenSearchExprIpValue(ipString)));
   }
 
   @Test
   void testHashCode() {
     assertNotNull(ipValue.hashCode());
   }
+
+  @Test
+  void testStringValue() {
+    assertEquals(ipString, ipValue.stringValue());
+  }
 }