private void configureApiToReturn(long[] projectIds) { var projects = projectIds.Select(projectId => { var project = Substitute.For <IProject>(); project.Id.Returns(projectId); project.Name.Returns(projectId.ToString()); return(project); }).ToList(); ProjectsApi .Search(Arg.Any <long>(), Arg.Any <long[]>()) .Returns(Observable.Return(projects)); }