[4286] Added a comment to Option4AddrLstTest.empty

src/lib/dhcp/tests/option4_addrlst_unittest.cc

@@ -1,4 +1,4 @@
-// Copyright (C) 2011-2015 Internet Systems Consortium, Inc. ("ISC")
+// Copyright (C) 2011-2016 Internet Systems Consortium, Inc. ("ISC")
 //
 // This Source Code Form is subject to the terms of the Mozilla Public
 // License, v. 2.0. If a copy of the MPL was not distributed with this
@@ -196,6 +196,7 @@ TEST_F(Option4AddrLstTest, assembly4) {
     );
 }
 
+// This test verifies that an option (e.g., mobile-ip-home-agent) can be empty.
 TEST_F(Option4AddrLstTest, empty) {
 
     scoped_ptr<Option4AddrLst> opt;