I have been changing the mocking framework used on a project I am planning to open source. Previously it had been using Typemock to mock out items in the TFS API. This had been working well but used features of the toolset that are only available on the licensed product (not the free version). As I don’t like to publish tests people cannot run I thought it best to swap to Microsoft Fakes as there is a better chance any user will have a version of Visual Studio that provides this toolset.

Most of the changes were straightforward but I hit a problem when I tried to run a test that returned a TFS IBuildDetails object for use inside an IronPython DSL.

My working Typemock based test was as follows

[Test]
     public void Can_use_Dsl_to_get_build_details()
     {
        // arrange
         var consoleOut = Helpers.Logging.RedirectConsoleOut();

         var tfsProvider = Isolate.Fake.Instance();
         var emailProvider = Isolate.Fake.Instance();
         var build = Isolate.Fake.Instance();

         var testUri = new Uri(“vstfs:///Build/Build/123”);
         Isolate.WhenCalled(() => build.Uri).WillReturn(testUri);
         Isolate.WhenCalled(() => build.Quality).WillReturn(“Test Quality”);
         Isolate.WhenCalled(() => tfsProvider.GetBuildDetails(null)).WillReturn(build);

       // act         TFSEventsProcessor.Dsl.DslProcessor.RunScript(@“dsltfsloadbuild.py”, tfsProvider, emailProvider);

        // assert
         Assert.AreEqual(“Build ‘vstfs:///Build/Build/123’ has the quality ‘Test Quality’” + Environment.NewLine, consoleOut.ToString());
     }

Swapping to Fakes I got

[Test]
     public void Can_use_Dsl_to_get_build_details()
     {
        // arrange
         var consoleOut = Helpers.Logging.RedirectConsoleOut();
         var testUri = new Uri(“vstfs:///Build/Build/123”);

         var emailProvider = new Providers.Fakes.StubIEmailProvider();
         var build = new StubIBuildDetail()
                         {
                             UriGet = () => testUri,
                             QualityGet = () => “Test Quality”,
                         };
         var tfsProvider = new Providers.Fakes.StubITfsProvider()
         {
             GetBuildDetailsUri = (uri) => (IBuildDetail)build
         };

         // act
         TFSEventsProcessor.Dsl.DslProcessor.RunScript(@“dsltfsloadbuild.py”, tfsProvider, emailProvider);
     

        // assert
         Assert.AreEqual(“Build ‘vstfs:///Build/Build/123’ has the quality ‘Test Quality’” + Environment.NewLine, consoleOut.ToString());
     }

But this gave me the error

Test Name:    Can_use_Dsl_to_get_build_details
Test FullName:    TFSEventsProcessor.Tests.Dsl.DslTfsProcessingTests.Can_use_Dsl_to_get_build_details
Test Source:    c:Projectstfs2012TFSTFSEventsProcessorMainSrcWorkItemEventProcessor.TestsDslDslTfsProcessingTests.cs : line 121
Test Outcome:    Failed
Test Duration:    0:00:01.619

Result Message:    System.MissingMemberException : ‘StubIBuildDetail’ object has no attribute ‘Uri’
Result StackTrace:   
at IronPython.Runtime.Binding.PythonGetMemberBinder.FastErrorGet`1.GetError(CallSite site, TSelfType target, CodeContext context)
at System.Dynamic.UpdateDelegates.UpdateAndExecute2[T0,T1,TRet](CallSite site, T0 arg0, T1 arg1)
at Microsoft.Scripting.Interpreter.DynamicInstruction`3.Run(InterpretedFrame frame)
at Microsoft.Scripting.Interpreter.Interpreter.Run(InterpretedFrame frame)
at Microsoft.Scripting.Interpreter.LightLambda.Run2[T0,T1,TRet](T0 arg0, T1 arg1)
at IronPython.Compiler.PythonScriptCode.RunWorker(CodeContext ctx)
at IronPython.Compiler.PythonScriptCode.Run(Scope scope)
at IronPython.Compiler.RuntimeScriptCode.InvokeTarget(Scope scope)
at IronPython.Compiler.RuntimeScriptCode.Run(Scope scope)
at Microsoft.Scripting.SourceUnit.Execute(Scope scope, ErrorSink errorSink)
at Microsoft.Scripting.SourceUnit.Execute(Scope scope)
at Microsoft.Scripting.Hosting.ScriptSource.Execute(ScriptScope scope)
at TFSEventsProcessor.Dsl.DslProcessor.RunScript(String scriptname, Dictionary`2 args, ITfsProvider iTfsProvider, IEmailProvider iEmailProvider) in c:Projectstfs2012TFSTFSEventsProcessorMainSrcWorkItemEventProcessorDslDslProcessor.cs:line 78
at TFSEventsProcessor.Dsl.DslProcessor.RunScript(String scriptname, ITfsProvider iTfsProvider, IEmailProvider iEmailProvider) in c:Projectstfs2012TFSTFSEventsProcessorMainSrcWorkItemEventProcessorDslDslProcessor.cs:line 31
at TFSEventsProcessor.Tests.Dsl.DslTfsProcessingTests.Can_use_Dsl_to_get_build_details() in c:Projectstfs2012TFSTFSEventsProcessorMainSrcWorkItemEventProcessor.TestsDslDslTfsProcessingTests.cs:line 141

If I altered my test to not use my IronPython DSL but call the C# DSL Library directly the error went away. So the issue lay in the dynamic IronPython engine – not something I am going to even think of trying to fix.

So I swapped the definition of the mock IBuildDetails to use Moq (could have used the free version of Typemock or any framework) instead of a Microsoft Fake Stubs and the problem went away.

So I had

[Test]
     public void Can_use_Dsl_to_get_build_details()
     {
         // arrange
         var consoleOut = Helpers.Logging.RedirectConsoleOut();
         var testUri = new Uri(“vstfs:///Build/Build/123”);

         var emailProvider = new Providers.Fakes.StubIEmailProvider();
         var build = new Moq.Mock();
         build.Setup(b => b.Uri).Returns(testUri);
         build.Setup(b => b.Quality).Returns(“Test Quality”);

         var tfsProvider = new Providers.Fakes.StubITfsProvider()
         {
             GetBuildDetailsUri = (uri) => build.Object
         };

        // act
         TFSEventsProcessor.Dsl.DslProcessor.RunScript(@“dsltfsloadbuild.py”, tfsProvider, emailProvider);

         // assert
         Assert.AreEqual(“Build ‘vstfs:///Build/Build/123’ has the quality ‘Test Quality’” + Environment.NewLine, consoleOut.ToString());
     }

So I have a working solution, but it is a bit of a bit of a mess, I am using Fake Stubs and Moq in the same test. There is no good reason not to swap all the mocking of interfaces to Moq. So going forward on this project I only use Microsoft Fakes for Shims to mock out items such as  TFS WorkItem objects which have no public constructor.