public async void ByAccountNumber_Not_Exists()
{
var mock = new ServiceMockFacade <IVendorRepository>();
mock.RepositoryMock.Setup(x => x.ByAccountNumber(It.IsAny <string>())).Returns(Task.FromResult <Vendor>(null));
var service = new VendorService(mock.LoggerMock.Object,
mock.RepositoryMock.Object,
mock.ModelValidatorMockFactory.VendorModelValidatorMock.Object,
mock.BOLMapperMockFactory.BOLVendorMapperMock,
mock.DALMapperMockFactory.DALVendorMapperMock,
mock.BOLMapperMockFactory.BOLProductVendorMapperMock,
mock.DALMapperMockFactory.DALProductVendorMapperMock,
mock.BOLMapperMockFactory.BOLPurchaseOrderHeaderMapperMock,
mock.DALMapperMockFactory.DALPurchaseOrderHeaderMapperMock);
ApiVendorResponseModel response = await service.ByAccountNumber(default(string));
response.Should().BeNull();
mock.RepositoryMock.Verify(x => x.ByAccountNumber(It.IsAny <string>()));
}