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));
        }