How to run unit tests in STAThread mode?

Question

I would like to test an app that uses the Clipboard (WindowsForms) and I need the Clipboard in my unit tests also. In order to use it, it should run in STA mode, but since the NUnit TestFixture does not have a main method, I don't know where/how to annotate it.

Answer 1

For NUnit 2.2, 2.4 (See simple solution below for 2.5):

Add an app.config file to the project containing your unit tests and include the following:

<?xml version="1.0" encoding="utf-8" ?>
<configuration>
    <configSections>
        <sectionGroup name="NUnit">
        <section name="TestRunner" type="System.Configuration.NameValueSectionHandler"/>
    </sectionGroup>
    </configSections>
    <NUnit>
        <TestRunner>
            <add key="ApartmentState" value="STA"/>
        </TestRunner>
    </NUnit>
</configuration>

You can verify that the apartment threading is STA with the following C# code:

if (Thread.CurrentThread.GetApartmentState() != ApartmentState.STA)
{
   throw new ThreadStateException("The current threads apartment state is not STA");
}