public void User_Cannot_Be_Removed_From_A_Group_Multiple_Times()
{
IUserRepository userRepo = Substitute.For<IUserRepository>();
IGroupRepository groupRepo = Substitute.For<IGroupRepository>();
userRepo.UserExists("fred").Returns(true);
groupRepo.GroupExists("testgroup").Returns(true);
groupRepo.UserIsAMember("fred", "testgroup").Returns(false);
UserController controller = new UserController(userRepo, groupRepo);
var result = controller.RemoveUserFromGroup("fred", "testgroup");
groupRepo.DidNotReceive().RemoveUserFromGroup("fred", "testgroup");
}