public void MapModelsReturnsSuccessForValidDataModelsWithoutLegacyRegions() { // Arrange var appRegistrationModel = ModelBuilders.ValidAppRegistrationModel(ModelBuilders.PathName); var legacyPathModel = ModelBuilders.ValidLegacyPathModel(ModelBuilders.PathName); IList <LegacyRegionModel>?legacyRegionModels = null; var validRegionModels = ModelBuilders.ValidRegionModels(); A.CallTo(() => fakeMapper.Map(legacyPathModel, appRegistrationModel)); A.CallTo(() => fakeMapper.Map <List <RegionModel> >(legacyRegionModels)).Returns(validRegionModels); // Act modelMappingService.MapModels(appRegistrationModel, legacyPathModel, legacyRegionModels); // assert A.CallTo(() => fakeMapper.Map(legacyPathModel, appRegistrationModel)).MustHaveHappenedOnceExactly(); A.CallTo(() => fakeMapper.Map <List <RegionModel> >(legacyRegionModels)).MustNotHaveHappened(); Assert.Null(appRegistrationModel.Regions); }