title: Unit tests code with Dns.GetHostEntry(hostNameOrIp) dependency
body: <p>I have code that uses <code>Dns.GetHostEntry(hostNameOrIp)</code> and I want to check scenario that one time this function return real values <strong>but</strong> in some time(when I decide) this function throw exception.<br>
  Currently I am using MSTest framework in visual studio 2010.
  Someone has idea what is the easiest way to achieve it?</p>