使用 Moq 进行单元测试失败

Question

I am new to the unit testing world so please spare me. The goal of the question is to test a class as mentioned below:

public class Engine
{      
    #region Members
    private EnumDefinition.EngineRunningState runningState;
    private ComponentController componentController;
    private static readonly Logger logger = LogManager.GetCurrentClassLogger();
    #endregion

    #region Constructor
    public Engine(ComponentController componentController)
    {
        this.componentController = componentController;

    }
    #endregion

    #region Properties
    public EnumDefinition.EngineRunningState RunningState
    {
        get
        {
            return runningState;
        }
        private set
        {
            if (value != runningState)
            {
                componentController.EngineRunningStateChangedEvent += OnEngineRunningStateChange;               
            }
        }
    }
    #endregion

    /// <summary>
    /// Start the Engine Request
    /// </summary>
    public void StartEngineRequest() 
    {
        // Check Engine Status
        if (runningState == EnumDefinition.EngineRunningState.Off)
        {
            componentController.SetEngineRequestToActive();
        }
        else if (runningState == EnumDefinition.EngineRunningState.Error)
        {
            logger.Trace("Engine Start Request Sent on a ENGINE ERROR!!!!!!");
        }
        else
        {
            logger.Trace("Engine Start Request, Engine is still ON");
        }

    }
    private void OnEngineRunningStateChange(object sender, EngineRunningStateArgs e)
    {
            runningState = e.runningStateofEngine;
    }
}

I want to test the public functions in Engine. Now I present my Test class:

[TestFixture]
public class EngineTest
{       
    [Test]
    public void StartEngineRequestTest()
    {
        Mock<ComponentController> mockComponentController = new Mock<ComponentController>();
        Mock<EngineRunningStateArgs> mockEngineRunningStateArgs = 
            new Mock<EngineRunningStateArgs>(EnumDefinition.EngineRunningState.On);
        var engineTest = new Engine(mockComponentController.Object);
        mockComponentController.Raise(mock => mock.EngineRunningStateChangedEvent += null, mockEngineRunningStateArgs.Object);              
        engineTest.StartEngineRequest();
    }
}

mt test fails giving an error as mentioned below: Result StackTrace: at Moq.Extensions.GetEvent[TMock](Action 1 eventExpression, TMock mock) at Moq.Mock 1.Raise(Action 1 eventExpression, EventArgs args) at AutoTugTest.EngineTest.StartEngineRequestTest() in C:\\GatewayController\\01 Working Copy\\GatewayComputer\\AutoTugTest\\EngineTest.cs:line 23 Result Message: System.ArgumentException : Expression is not an event attach or detach, or the event is declared in a class but not marked virtual.

I have no idea what is happening. I just want to throw an event from ComponentController with event name as EngineRunningStateChangedEvent with an event argument. Please suggest.

Answer 1

Moq can only mock virtual members. It's good at mocking interfaces because there's no implementations, but if you want to mock a concrete class the members that you mock will need to be virtual. That lets Moq wrap the 'real' implementation with it's own.