Thank you for this answer! I was searching on google like crazy and nothing solved my problem, this was the only thing that worked. For the record, here is a code snippet of the solution:

public class SomeClassTest {

     @Test

     public void testSomeMethod() throws Exception{

          new FacesRequest(){

               @Override

               protected void applyRequestValues() {

                    setParameter("someRequestParameter", "1234");

               }

               @Override

               protected void invokeApplication() throws Exception {

                    invokeMethod("#{someClass.someMethod()}");

                    Assert.assertTrue(true);

               }

          }.run();

     }

}

@Name("someClass")

@Scope(ScopeType.CONVERSATION)

@AutoCreate

@PerNestedConversation

public class SomeClass implements java.io.Serializable {

     @RequestParameter

     String someRequestParameter;

     public void loadData() {

          System.out.println("someRequestParameter: " + someRequestParameter);

     }
}