public async System.Threading.Tasks.Task ShallReturnCalendarEventsFromProviderAsync() { calendarEventsProviderMock.Setup(p => p.GetEventsInMonthAsync(It.IsAny <int>(), It.IsAny <int>())).Returns(() => { var cal = new CalendarEvent() { Subject = "MySubject", StartDate = new DateTime(2020, 6, 1), EndDate = new DateTime(2020, 6, 1) }; var result = new ConcurrentBag <CalendarEvent>(); result.Add(cal); return(Task.FromResult <ConcurrentBag <CalendarEvent> >(result)); }); var result = await calendarController.GetEventsInMonthAsync(2020, 6); calendarEventsProviderMock.Verify(p => p.GetEventsInMonthAsync(2020, 6), Times.Once); Assert.That(result.Count, Is.EqualTo(1)); Assert.That(result.First().EndDate, Is.EqualTo(new DateTime(2020, 6, 1))); }