The Xen Node.js Library by Pirlot Nicolas provides a module to interact with Citrix XenServer API, and is designed to let users make XML-RPC calls with Xen's API. The Xen API, or XAPI, gives developers tools and an interface for the remote management of virtualized guests running on a Xen-enabled host.
One of the challenges with building an application these days is the number of dependencies that application will actually have on other applications. Ideally in order to know how that application will actually perform application developers would be able to test their application against the application it depends on running in production. The odds of that happening, however, are slim to none, especially if that other application is running as a cloud service that has to be always available to end users.