This week was short work-wise, and went by quickly. Last week was hectic and long. Me and my colleague Truls gave a seminar on NHibernate, a little ActiveRecord and some of the new MS OR stuff. Then I spent three days with another consulting company, showing them the ins and outs of NHibernate and sprinkling just a little WCF on the last day. In so doing, I caught myself serving out some code that I have used. Normally, I don't dish out any code here, but this might be useful to some:

It's a small WCF test helper that I have used to do explorative testing of WCF and even more so for integrative smoke tests of WCF services.

There is a zip attached that contains one vs.net 2005 project with a WCF hello world and one nunit test that runs that service. That test is an integration test, it cranks up the whole WCF machinery. Most of my WCF integration tests (all, in fact) do not test any concurrency issues. They are more simple smoke tests that everything seems to work as expected. What I usually want is to test the machinery but have one instance invoked, so that I can execute some assertions on the results using that instance afterwards.

Usually, you will not implement your WCF service as a singleton (although it is one of the instancing modes), for one of several reasons - scalability for example. Using the other instancing modes means that you (by default) do not control construction of your the instance that gets to serve the requests, and thus in a test situation, we do not have a reference to the instance used by WCF. One way around this is to create a custom instance provider. The instance provider in WCF (class implementing IInstanceProvider, the default being a private class in InstanceBehavior, reflect it) is responsible for supplying new service instances. I won't talk about it here, suffice it to say that my SingletonInstanceProvider simply returns one (settable) instance each time, thus making the service a singleton. It is a service behavior that we add to the servicehost description.

Why do this? Simply so that I can implement my service using an instancing mode that I want, but still run simple smoke tests on it. It is one solution, there are doubtless many others, if you have a better one, please give me a shout.

So, the testhelper or testharness that is enclosed actually does a couple of things. I won't talk about them in detail, this is roughly it:

• Provide a simple way to create and start a service host and get a client to run tests against it.
• Provide a way for tests to share services, so that the WCF machinery does not need to be restarted.
• Get the services set up using the SingletonInstanceProvider easily
• Allow test to access host before it is started to modify/further configure
  ( this is why you see castle in there, the client (a dynamic proxy wrapper) is actually a proxy that opens the service late/JIT )

You use it like so:

IMessageOfTheDay client1 = GetClient

   .For<IMessageOfTheDay>()

   .Using(new NetTcpBinding())

   .Running(serviceInstance);

This sets up a service host for the IMessageOfTheDay service contract, using the netTcpBinding (optional, default is named pipes since it is the fastest) and running the instance supplied. See the demotest.

Comments welcome. Btw, this uses my singleton implementation, I'll make a note of that tomorrow, but it's simple.

Questions: Has anyone seen another wcf test harness like this? I usually do all my network integration testing using some thread harness with synchronization between, and did my WCF testing in a similar (not the same) way. This harness simplified things quite a bit.

BTW: Most of the code is in one file; TestHelper.cs. It's a bit unwieldly, sorry, but easier to copy - you still need the singleton.cs though. I may update later if I get time.

Again, the download is here.