Hi Charlie, I've committed some changes regarding the build scripts mainly. Here's what I've done: - added "net-4.5" support to NAnt as described in the SO question you linked - created a .net 4.5 assembly containing tests for async. Created a .net 4.5 assembly containing fixtures which are run programmatically by the former. The build file of these two assemblies forces the "nant.settings.currentframework" property to "net-4.5" as they can only be built if 4.5 is installed (regardless of the target framework of the build itself) - modified the build scripts to support net-4.5 as a target framework (this includes setting some properties and defining the precompiler conditionals CLR_4_0, NET_4_5, CS_5_0 - modified the code with precompiler conditionals to include NET_4_5 where meaningful - modified the build scripts so that even if you target other versions of the .NET fx BUT .NET 4.5 is installed, then: - the two assemblies above are built - the tests contained therein are run This required adding a new NUnit test project containing the 4.5 test assembly in addition to all the others, without any "runtimeFramework" attribute specified so that the console will be able to spawn an agent when it's not itself built for 4.5 but the test assemblies are there. I hope this makes sense. I admit that I'm not super-happy with the solution because it involves a lot of conditionals, mainly in the build scripts, all over the place, but I'm not sure we can do much better with what we have right now in V2. The changes are not many though, so it should not take you long to figure out what I did exactly. Simone On Wed, Oct 3, 2012 at 7:29 AM, Charlie Poole