private async void BeUniqueByName_Update_Not_Exists()
        {
            Mock <ITenantRepository> tenantRepository = new Mock <ITenantRepository>();

            tenantRepository.Setup(x => x.ByName(It.IsAny <string>())).Returns(Task.FromResult <Tenant>(null));
            var validator = new ApiTenantRequestModelValidator(tenantRepository.Object);

            await validator.ValidateUpdateAsync(default(string), new ApiTenantRequestModel());

            validator.ShouldNotHaveValidationErrorFor(x => x.Name, "A");
        }