[Fact] // 2. async Task<IEnumerable<CityListServiceModel>> AllCitiesByCountryAsync(int id) public async void AllCitiesByCountryAsync_ShouldReturnModelCollectionOfAllByCountry() { // Arrange var country = CountryCreator.Create(); var city = CityCreator.Create(country.Id); var city2 = CityCreator.Create(country.Id); var city3 = CityCreator.Create(country.Id); var country2 = CountryCreator.Create(); var city4 = CityCreator.Create(country2.Id); var city5 = CityCreator.Create(country2.Id); await this.Context.Countries.AddRangeAsync(country, country2); await this.Context.Cities.AddRangeAsync(city, city2, city3, city4, city5); await this.Context.SaveChangesAsync(); var service = new CityService(this.Context); // Act var result = await service.AllCitiesByCountryAsync(country2.Id); // Assert result.Should().AllBeOfType <CityListServiceModel>(); result.Should().HaveCount(2); }