The APP Test Client now has its own project page, and a new version is now available. There have been updates to support the latest version of the APP and some more features to help in debugging your APP server, such as the "Export..." button which writes a diagnostics.txt file with the contents of the diagnostics window.
The biggest feature of this release is the availibility of a Windows executable. You can now download and run the APP Test Client without having to install Python or wxPython. In addition, the executable is pre-configured to work with my public APP server so you have something to work with initially, but the whole idea is that you update the config file and do some interop testing against your own APP server implementation.
Anything you publish to the APP Test Site will show up here.