Beautiful Testing

Testing Session Initialization

By looking at both the single- and multistage request/response protocols from the previous sections, we covered most of the XMPP protocols out there. Although the level of testing for these protocols was already rather high, some protocols are still so complex that even testing at the level of “abstract” payloads results in too much clutter for a beautiful test. These are typically protocols that have a complex state diagram, and possibly even require user input during the process. We therefore bring in a higher level of testing: scenario testing.

One of the most complex protocols in XMPP is session initialization. Session initialization in an IM client involves creating a connection to the server; negotiating parameters of the connection (e.g., using stream compression for lower bandwidth consumption, encrypting the stream for better security, and so on); and finally authenticating with the server (typically involving sending a username and password to the server). Which parameters to negotiate with the server depends on what features the client and the server support, and also on the user preferences of the client. For example, a server might not support stream encryption; depending on whether the user has stated that he only wants to communicate over an encrypted connection, the client should either report an error or fall back on an unencrypted connection, respectively.

Testing all the possible code paths in session initialization requires a concise ...