Do not mock the proclaimers... https://twitter.com/#!/ianfnelson/status/202379439164768258

gistfile1.cs

[Test]
public void proclaimer_falls_down_at_door()
{
    var proclaimer = nSubstitue.For<IProclaimer>();
    proclaimer.Walk500Miles().Returns("One thousand miles walked");

    var door = nSubstitue.For<IDoor>();

    var sut = new ProclaimerGoesAboutHisBusinessService(proclaimer, door);

    sut.Execute();

    door.Received().SomeoneFellDown(proclaimer);

}