無法驗證Moq'd func被調用

Question

我試圖用起訂量來模擬一個Func<Tin, Tout>並驗證它被調用（引用）

我目前擁有的代碼是：

var handlers = new List<ICallBridgeHandler>(); 
var stationIdReader = new Mock<IStationIdReader>(); 
var loggerCreator = new Mock<Func<Type, ILogger>>(); 
loggerCreator.Setup(x => x.Invoke(typeof(Service))).Returns<ILogger>(null); 

loggerCreator.Verify(x => x.Invoke(It.IsAny<Type>()), Times.Never); 
var sut = new Service(stationIdReader.Object, handlers, loggerCreator.Object); 
loggerCreator.Verify(x => x.Invoke(typeof(Service)), Times.Once); 
Assert.IsNotNull(sut); 

但這是吹了除了：

Result StackTrace: 
at Moq.ExpressionExtensions.GetCallInfo(LambdaExpression expression, Mock mock) 
at Moq.Mock.<>c__DisplayClass1c`2.<Setup>b__1b() 
at Moq.PexProtector.Invoke[T](Func`1 function) 
at Moq.Mock.Setup[T,TResult](Mock`1 mock, Expression`1 expression, Condition condition) 
at Moq.Mock`1.Setup[TResult](Expression`1 expression) 
at Tests.ConstructorRetrievesLoggerFromCreator() in ... 

Result Message: 
Test method Tests.ConstructorRetrievesLoggerFromCreator threw exception: 
System.InvalidCastException: Unable to cast object of type 
'System.Linq.Expressions.InstanceMethodCallExpressionN' to type 
'System.Linq.Expressions.InvocationExpression'. 

任何人都可以幫助，我需要能夠檢查構造函數調用Func。

N.B.我試圖刪除設置步驟，因爲我不關心此測試的返回值，並且我在驗證呼叫中遇到同樣的問題。

很顯然，我可以注入返回給定值的具體的FUNC鍵，以某種方式查詢該值，但是我的服務類的樣子：

public class Service 
{ 
    private readonly ILogger _logger; 

    [ImportingConstructor] 
    public Service([Import("GetLogger")]Func<Type, ILogger> loggerCreator) 
    { 
     if (loggerCreator == null) 
      throw new ArgumentNullException(nameof(loggerCreator)); 

     _logger = loggerCreator.Invoke(GetType()); 
    } 
} 

因此，沒有改變我的課，我不能看到成員變量_logger所以我無法驗證loggerCreator已被調用，這就是我想驗證的。

Answer 1

沒有必要模擬該功能。創建一個Func變量並在其中保留一個計數器以保持跟蹤。

[TestMethod] 
public void Func_Should_Be_Invoked_Once() { 
    //Arrange 
    var handlers = new List<ICallBridgeHandler>(); 
    var stationIdReader = new Mock<IStationIdReader>(); 
    var mockLogger = new Mock<ILogger>(); 
    int loggerCreaterInvokeCalls = 0; 
    Func<Type, ILogger> loggerCreator = (type) => { 
     loggerCreaterInvokeCalls++; 
     return mockLogger.Object; 
    }; 
    //Act 
    var sut = new Service(stationIdReader.Object, handlers, loggerCreator); 
    //Assert 
    Assert.IsNotNull(sut); 
    Assert.AreEqual(1, loggerCreaterInvokeCalls); 
} 

參考：Using Moq to Mock a Func<> constructor parameter and Verify it was called twice