public async Task add_trip_async_should_invoke_repository_method()
        {
            var mockedRepository       = new Mock <ITripRepository>();
            var customerRepository     = new Mock <ICustomerRepository>();
            var mockedMapper           = new Mock <ITraveloMapper>();
            var mockedDateTimeProvider = new MockedDateOffsetProvider(DateTimeOffset.Now);

            var tripService =
                new TripService(mockedRepository.Object, customerRepository.Object, mockedMapper.Object,
                                mockedDateTimeProvider);

            var now = DateTimeOffset.Now;
            await tripService.AddTripAsync(new TripDTO()
            {
                StartDate   = now, EndDate = now + TimeSpan.FromDays(7), Name = "Trip name", Destination = "Berlin",
                Description = "Long trip"
            });

            mockedRepository.Verify(x => x.AddTripAsync(It.IsAny <Trip>()), Times.Once());
        }