Explicitly call static constructor

I want to write unit test for below class.
If name is other than "MyEntity" then mgr should be blank.
Negative Unit test
Using Manager private accessor I want to change name to "Test" so that mgr should be null. And then will verify the mgr value. To achieve this, I want to explicitly call the static constructor but when I call the static constructor using

Manager_Accessor.name = "Test"
typeof(Manager).TypeInitializer.Invoke(null, null); 

name is always set to "MyEntity" how to set name to "Test" and invoke the static constructor.

public class Manager
{        
        private static string name= "MyEntity";

        private static object mgr;

        static Manager()
        {
            try
            {
                mgr = CreateMgr(name);
            }
            catch (Exception ex)
            {
                mgr=null;
            }
        }
}