private async void BeUniqueByName_Update_Not_Exists() { Mock <IWorkerRepository> workerRepository = new Mock <IWorkerRepository>(); workerRepository.Setup(x => x.ByName(It.IsAny <string>())).Returns(Task.FromResult <Worker>(null)); var validator = new ApiWorkerRequestModelValidator(workerRepository.Object); await validator.ValidateUpdateAsync(default(string), new ApiWorkerRequestModel()); validator.ShouldNotHaveValidationErrorFor(x => x.Name, "A"); }