Here is the solution to my previous posting Could not find file ‘Microsoft.Windows.CommonLanguageRuntime error for test projects.
As always it is simple when you know how. You simply uncheck the Enable ClickOnce security settings-checkbox under Projects -> Properties -> Security.
A better solution is the extract the code that is to be tested to an own project, but I’ll use the above for now. We’re only using ClickOnce for testing environments.