I found a better solution for my problems with the build server and the assembly that wasn’t copied to the out directory. You can register which additional items that shall be copied to the out directory in a unit test with the attribute DeploymentItem. I annotated my unit test with the following line of code.
Thereafter I could remove my dummy code and the unit tests worked as expected. More information can be found at http://msdn.microsoft.com/en-us/library/ms182475(VS.80).aspx.