We just released the version 0.20 of Pex. This version brings a Beavers, an extension of Stubs to write models, a global event view in Visual Studio and many bug fixes. Beavers are a small programatic models that build upon Moles…

• Beavers: With stubs and moles, we provided a framework to write record/replay tests (i.e. mock-based tests) against any .NET type, interface or not. Beavers take you to the next level and allow you to write simple implementations with behavior (hence the ‘B’eaver) that can be used to replace the external system during testing. The benefit of using Beavers is that the resulting test cases are much more robust to code changes since the tests specify the state of the system, rather than a sequence of method calls and outcomes. We will talk a lot about Beavers in the future. Let’s take a look at an example. The following snippet uses Moles to redirect the constructor of a Bank class, then sets up the GetAccountById(int) method to return an instance of IAccount, etc… This is a typical test that is based record and replay. The problem with this technique is that it is really fragile with respect to code changes: if the code calls different methods, the test will break.
  
  The same behavior can be specified using Beavers. Beaver are simple implementations that simulate that capture enough behavior of the original code for testing. Using Beavers, one can specify the state of the system. The functional behavior is re-factored away in a Beaver class and reused in all tests!
  
• Global Event View: when executing multiple explorations, it was cumbersome to go through each exploration to investigate the events (instrumentation, object creation, etc…). We have added a view in the Pex Explorer tree view that centralizes the events for the entire run.
  
• Beavers for SharePoint: The samples that come with Pex contains a number of Beavers for the SharePoint object model (SPList, SPListItem, SPField, etc…) that should help you get started with testing SharePoint with Beavers. As an example, you can compare a mole-based test (left) and a beaver-based test (right) for a simple SharePoint service:
  
• Bug fixes and Improvements:
  • The HostType crashes non-deterministically.
  • Visual Studio 2010 crashes when loading with a ‘DocumentSite already has a site’ error message.
  • The Stubs code generator uses a lot of memory and may crash Visual Studio. The Stubs generator now runs out of process and does not take down Visual Studio when it runs out of memory.
  • The Stubs code generator detects version changes of the Stubs framework to regenerate the stubs assemblies.
  • The Pex execution produces less warnings. We’ve reviewed our warnings and moved some, who did not matter, as messages.
  • When a Contract.Requires is failed multiple time in a stacktrace, do not allow it.
  • The object factory guesser has partial support for internal types and internal visible to (signed assemblies not supported).
  • The ‘add’ and ‘remove’ of events can be moled to deal with events.
  • Digger does not work in Visual Studio 2010 when no test project exists.
• Breaking Changes: The Beavers introduced a number of refactoring that might impact users of Stubs and Moles. The .stubx file should regenerate themselves automatically, otherwise right click on the file and select ‘Run Custom Tool’.
  • Most types of the Stubs framework have been moved to sub namespaces.
  • IStubBehavior was renamed to IBehavior
  • StubFallbackBehavior was renamed to BehaviorFallbackBehavior
  • PexChooseAsStubFallbackBehaviorAttribute was renamed to PexChooseAsBehavedFallbackBehaviorAttribute
  • PexChooseStubBehavior was renamed to PexChooseBehavedBehavior
  • PexExpectedGoalsAttribute and PexGoal.Reached(…) were renamed and refactored into PexAssertReachEventuallyAttribute and PexAssert.ReachEventually(…);