public void GetTerritories_NoTerritoriesFound_ReturnsTerritories(
            [Frozen] Mock <IReferenceDataApiClient> referenceDataApiClient,
            ReferenceDataService sut
            )
        {
            //Arrange
            referenceDataApiClient.Setup(x => x.GetTerritoriesAsync())
            .ReturnsAsync((List <Territory>)null);

            //Act
            Func <Task> func = async() => await sut.GetTerritoriesAsync();

            //Assert
            func.Should().Throw <ArgumentNullException>()
            .WithMessage("Value cannot be null. (Parameter 'territories')");
        }
        public async Task GetTerritories_TerritoriesFound_ReturnsTerritories(
            [Frozen] Mock <IReferenceDataApiClient> referenceDataApiClient,
            List <Territory> territories,
            ReferenceDataService sut
            )
        {
            //Arrange
            referenceDataApiClient.Setup(x => x.GetTerritoriesAsync())
            .ReturnsAsync(territories);

            //Act
            var response = await sut.GetTerritoriesAsync();

            //Assert
            response.Count.Should().Be(3);
        }