Using xUnit 1.5 with .NET 4.0 RTW

After a bit of tinkering, I finally managed to find the sweet spot for getting xUnit 1.5 to run (without errors) with projects targeted at the new .NET 4.0 Framework.

After initial solution conversion, if you run your tests with xunit.console.x86.exe (or the 64-bit version, I’m assuming), you’ll face the following helpful error:

System.BadImageFormatException: Could not load file or assembly 'Assembly.Test.dll' 
or one of its dependencies. This assmbly is built by a runtime newer than the 
currently loaded runtime and cannot be loaded.
File name: 'J:\projects\Framework\build\Assembly.Test.dll'
   at System.Reflection.AssemblyName.nGetFileInformation(String s)
   at System.Reflection.AssemblyName.GetAssemblyName(String assemblyFile)
   at Xunit.Sdk.Executor..ctor(String assemblyFilename)
   at Xunit.ExecutorWrapper.RethrowWithNoStackTraceLoss(Exception ex)
   at Xunit.ExecutorWrapper.CreateObject(String typeName, Object[] args)
   at Xunit.ExecutorWrapper..ctor(String assemblyFilename, String configFilename,
      Boolean shadowCopy)
   at Xunit.ConsoleClient.Program.Main(String[] args)

What?  BadImageFormatException?  But the bitness didn’t change!

@markhneedham blogged last year how to fix the problem: updating the config files for xunit to “support” the new version.  That worked then, but the version numbers have changed.

Here’s what the new configuration files need to include:

	<startup uselegacyv2runtimeactivationpolicy="true">
		<supportedruntime version="v4.0.30319" />
	</startup>

The useLegacyV2RuntimeActivationPolicy attribute ensures that the latest supported runtimes are loaded. For my projects, this seems to keep Oracle.DataAccess.dll and System.Data.Sqlite.dll (both x86 libraries) happy.

The supportedRuntime element denotes the current version of .NET 4.0 (30319 is the RTM build).

After that, everything runs like a champ!

xUnit.net console test runner (32-bit .NET 4.0.30319.1)
Copyright (C) 2007-9 Microsoft Corporation.

xunit.dll:     Version 1.4.9.0
Test assembly: Assembly.Test.dll

Total tests: 397, Failures: 0, Skipped: 0, Time: 7.508 seconds