public When_OpportunityService_Is_Called_To_Get_Referrals()
        {
            var config = new MapperConfiguration(c => c.AddMaps(typeof(OpportunityMapper).Assembly));
            var mapper = new Mapper(config);

            var opportunityRepository           = Substitute.For <IOpportunityRepository>();
            var opportunityItemRepository       = Substitute.For <IRepository <OpportunityItem> >();
            var provisionGapRepository          = Substitute.For <IRepository <ProvisionGap> >();
            var googleMapApiClient              = Substitute.For <IGoogleMapApiClient>();
            var opportunityPipelineReportWriter = Substitute.For <IFileWriter <OpportunityReportDto> >();
            var dateTimeProvider = Substitute.For <IDateTimeProvider>();

            var mockDbSet = new ReferralListBuilder()
                            .Build()
                            .AsQueryable()
                            .BuildMockDbSet();

            //var mockDbSet = new List<Domain.Models.Referral>
            //    {
            //        new Domain.Models.Referral
            //        {
            //            ProviderVenue = new Domain.Models.ProviderVenue
            //            {
            //                Postcode = "AA1 1AA",
            //                Provider = new Domain.Models.Provider
            //                {
            //                    Name = "Provider1"
            //                }
            //            }
            //        }
            //    }
            //    .AsQueryable()
            //    .BuildMockDbSet();

            _referralRepository = Substitute.For <IRepository <Domain.Models.Referral> >();

            _referralRepository.GetManyAsync(
                Arg.Any <Expression <Func <Domain.Models.Referral, bool> > >())
            .Returns(mockDbSet);

            var opportunityService = new OpportunityService(mapper, opportunityRepository, opportunityItemRepository,
                                                            provisionGapRepository, _referralRepository, googleMapApiClient,
                                                            opportunityPipelineReportWriter, dateTimeProvider);

            _referralDtos = opportunityService.GetReferralsAsync(OpportunityItemId).GetAwaiter().GetResult();
        }