public void Should_remove_crew_members() { var place = new PlaceMock(); var crewMemberThatMustStay = new Pilot("pilot name"); var crewMembersThatMustBeRemoved = new List <CrewMember> { new Policeman("policeman name"), new Prisoner("prisoner name"), }; var crewMembers = new List <CrewMember>(); crewMembers.Add(crewMemberThatMustStay); crewMembers.AddRange(crewMembersThatMustBeRemoved); place.Board(crewMembers); place.Remove(crewMembersThatMustBeRemoved.First(), crewMembersThatMustBeRemoved.Last()); Assert.Contains(crewMemberThatMustStay, place.CrewMembers); Assert.Single(place.CrewMembers); }