[ONOS-3222] Implement toString method for each Packet class

Change-Id: I17d72338d4202117d08b3dca9463be35a87a0c1e
diff --git a/utils/misc/src/test/java/org/onlab/packet/UDPTest.java b/utils/misc/src/test/java/org/onlab/packet/UDPTest.java
index ba453f6..4b83897 100644
--- a/utils/misc/src/test/java/org/onlab/packet/UDPTest.java
+++ b/utils/misc/src/test/java/org/onlab/packet/UDPTest.java
@@ -18,6 +18,7 @@
 
 package org.onlab.packet;
 
+import org.apache.commons.lang3.StringUtils;
 import org.junit.BeforeClass;
 import org.junit.Test;
 
@@ -131,4 +132,18 @@
         assertTrue(udp1.equals(udp1));
         assertFalse(udp1.equals(udp2));
     }
+
+    /**
+     * Tests toString.
+     */
+    @Test
+    public void testToStringUdp() throws Exception {
+        UDP udp = deserializer.deserialize(bytePacketUDP4, 0, bytePacketUDP4.length);
+        String str = udp.toString();
+
+        assertTrue(StringUtils.contains(str, "sourcePort=" + 0x50));
+        assertTrue(StringUtils.contains(str, "destinationPort=" + 0x60));
+        assertTrue(StringUtils.contains(str, "length=" + (short) 8));
+        assertTrue(StringUtils.contains(str, "checksum=" + (short) 0x7bda));
+    }
 }