The landscape of modern enterprise IT environments is that a large number of distributed software systems interact and cooperate with each other to support daily business operations. With the prevalence of cloud computing, the level of system connectivity increases further. The large scale of such an environment makes it difficult to test a system's quality attributes such as performance and scalability before it is actually deployed in the production environment. Under the currently dominant iterative and incremental software development paradigm, this difficulty is even more pronounced when the quality attributes of an enterprise system need to be examined and evaluated at early stages but a large part of its operating environment is not available or accessible. In this paper, we present a Coloured Petri nets (CPN) based system behaviour emulation approach and a lightweight emulated testing framework for provisioning a virtual deployment testing environment for an enterprise software system, so that its quality attributes, especially scalability, can be evaluated without physically connecting to the real production environment. It is worth noting that the focus of this work is on the testing environment which enables virtual system deployment and testing, instead of being on the research topic of deployment test. CPN and its associated design and simulation tools have been used and integrated to model and execute the behaviour of those cooperating endpoint systems that an enterprise software system interacts with. We have successfully implemented an industry standard protocol Lightweight Directory Access Protocol in our approach and applied it in testing the scalability of a real-world enterprise application, CA Technologies' IdentityManager. A thorough in-lab performance study has also been conducted to examine the capacity and scalability of this approach.