Switch to checkNotNull

Change-Id: Ie34d783d5dcb0e6f71fd6155c14aaaaf47048bcc
diff --git a/src/test/java/net/onrc/onos/core/util/SwitchPortTest.java b/src/test/java/net/onrc/onos/core/util/SwitchPortTest.java
index 1c01e8f..2832dc1 100644
--- a/src/test/java/net/onrc/onos/core/util/SwitchPortTest.java
+++ b/src/test/java/net/onrc/onos/core/util/SwitchPortTest.java
@@ -30,7 +30,7 @@
     /**
      * Tests to confirm constructors input validation.
      */
-    @Test(expected = IllegalArgumentException.class)
+    @Test(expected = NullPointerException.class)
     public void testSwitchPortDpidPortNumberFailOnNull1() {
         new SwitchPort(null, PORT_NUM);
     }
@@ -38,7 +38,7 @@
     /**
      * Tests to confirm constructors input validation.
      */
-    @Test(expected = IllegalArgumentException.class)
+    @Test(expected = NullPointerException.class)
     public void testSwitchPortDpidPortNumberFailOnNull2() {
         new SwitchPort(DPID, null);
     }