WPF: writing smoke tests using ViewModels

Question

I am considering to write smoke tests for our WPF application. The question that I am faced is: should we use UI automation( or some other technology that creates a UI script), or is it good enough to use ViewModels directly (after all the viewmodels were created to make unit testing easier in a first place).

Answer 1

There's no reason why you can't write unit tests for your ViewModels if they're properly separated from your Views.

A smoke test is a test that actually fires up your application and checks that it works and (for an application with a UI) UI automation is the way to go for that.

Answer 2

We used to write our integration tests (smoke tests if you like) using the ViewModels directly. It worked, but we did have to deal with some interesting threading issues: what happens, for example if your ViewModel causes a Message Box to be shown - how does your test close the Message box? We had to make sure that our application was running on one thread and our tests on another.

We've now moved over to UIAutomation and those kind of problems go away because your tests and the application are explicitly running in two separate processes. There is a bit of a learning curve involved, but UIAutomation isn't as scary as it first appears: I've written a tutorial that might help you get started - follow the link, and you'll also find a few helper methods that tame the UI Automation API somewhat.