Microsoft has released two white papers for Lync Serverr 2013. The first focuses on virtualization and the second on stress testing:
This paper provides guidance for deploying Lync Server 2013 on virtual servers. It includes recommendations for the configuration of host servers and guest servers, key health indicators to watch during testing and deployment, and observations from Microsoft performance testing of Lync Server 2013 in a virtual environment.
To validate the capacity planning requirements of a Lync Server 2013 deployment, we recommend that you perform a stress testing exercise using The Lync Server 2013 Stress and Performance Tool (LSS). This document will take you through the steps required to plan and conduct a Lync Server stress testing exercise.