在編寫“驗證”測試方法時顯示“未執行調用”錯誤

我們有一個服務正在另一個服務中使用：

namespace ConsoleCalculator.Services
{
    public interface ICalculatorService
    {
        int GetLineCount(string inputLineCount);
    }
}

namespace ConsoleCalculator.Services
{
    public class CalculatorService : ICalculatorService
    {
        private readonly ICalculatorValidationService _calculatorValidationService;

        public CalculatorService(ICalculatorValidationService calculatorValidationService)
        {
            _calculatorValidationService = calculatorValidationService;
        }

        public int GetLineCount(string inputLineCount)
        {
            _calculatorValidationService.ValidateLineCount(inputLineCount);
            return Convert.ToInt32(inputLineCount);
        }
    }
}

現在，我們需要為所需服務編寫一個測試：

namespace ConsoleCalculator.Test.Services
{
    public class CalculatorServiceTest
    {
        private Mock<ICalculatorService> _calculatorService = new Mock<ICalculatorService>();
        private Mock<ICalculatorValidationService> _valculatorValidationService = new Mock<ICalculatorValidationService>();
        public CalculatorServiceTest()
        {
            _valculatorValidationService
              .Setup(q => q.ValidateLineCount(It.IsRegex("[^0-9]")))
              .Throws(new Exception());

            _calculatorService
                .Setup(q => q.GetLineCount(It.IsRegex("[^0-9]")))
                .Throws(new Exception());
        }


        [Fact]
        public void When_Input_Not_A_Number_Should_Return_Exception()
        {
            Assert.Throws<Exception>(() => _calculatorService.Object.GetLineCount("123a"));
        }

        [Fact]
        public void When_Call_Method_Should_Call_Exactaly_One_ValidateLineCount_Method()
        {
            _calculatorService.Object.GetLineCount(It.IsAny<string>());
            _valculatorValidationService.Verify(x => x.ValidateLineCount(It.IsAny<string>()), Times.Once);
        }
    }
}

編寫第二個測試的目的是確保我的測試服務被調用一次。但在運行測試時，我看到以下錯誤：

Moq.MockException：需要對模擬進行一次調用，但調用次數為0次：x=>x.ValidateLineCount(It.IsAny())