Attempted re-targeting of the project has been canceled. To be able to target your test project to .NET Framework 3.5, you must use the steps documented at the following Microsoft Web site:
Link
This link takes you to a page that gives you instructions on how to re target for .NET Framework 3.5.
How To Re target Visual Studio Test Projects for .NET 4 Platform Update
Right click on the project and select Unload Project
Right click on the unloaded project and select Edit (name of project)
Change the target framework version to v4.0.1
Reload the project and you are good to go.