public async Task ShouldReturnEntityCheckResponse() { //Assert var response = "{ 'result': { 'requestId': '123' } }"; var selectedSpecificationObject = new CheckSpecificationData { SelectedSpecification = "3245174504", BankAccount = "49635393242218223941769740" }; customHttpClient.Setup(x => x.GetStringAsync(It.IsAny <string>(), It.IsAny <Dictionary <string, string> >())).Returns(Task.FromResult(response)); //Act var action = await subjectService.CheckSubject(selectedSpecificationObject, CheckBySpecification.Nip, DateTime.Today); //Assert action.Should().BeOfType(typeof(EntityCheckResponse)); }