如何在“ Return”中设置模拟为Moq的out参数的值？

Question

I've some trouble while configuring my Moq.

I've a mockup with a method that has out parameter. This out parameter is really used, and I need to populate it with some meaningful value depending on the parameter I receive.

Currently, I've been unable to do this, is it possible? How?

Here is my current status:

Mock<IMyMock> _mock = new Mock<IMyMock>();
bool someFlag= false;
_mock.Setup(m=>m.GetSomething(It.IsAny<DateTime>(), It.IsAny<DateTime>(), out someFlag))
     .Returns((DateTime start, DateTime end, bool someFlagInternal)=>{
        IEnumerable<SomeOtherClass> otherClasses = GenerateMockedData(start, end);
        //Assign something to someFlag, depending on start and end
        someFlag=true;//This has no effects
     }) ;
new SomeController(_mock.Object);

In my SomeController , on a specific method, my real-non-mocked code calls it:

public class SomeController{}
    private IMyMock _someObjectThatWeDontKnowIsAMock;
    public SomeController(IMyMock someObjectThatWeDontKnowIsAMock) {
        _someObjectThatWeDontKnowIsAMock= someObjectThatWeDontKnowIsAMock;
    }

    private void ComputeNext() {
        Tuple<DateTime, DateTime> times = ComputeNextTimes();
        bool hasOverlap;
        IEnumerable<SomeOtherClass> otherClassesInstances = _someObjectThatWeDontKnowIsAMock.GenerateMockedData(times.Data1, times.Data2, out hasOverlap);
        if(hasOverlap) {
            //...
        }
    }
}

Every time I call my mock, it seems to returns the first value of someFlag , even if it is a static field that I modify.

Answer 1

The problem you are having is because the instance of the out parameter in the setup is different to the instance actually being used when exercising the test.

Taken from Moq Quickstart documentation

callbacks for methods with ref / out parameters are possible but require some work (and Moq 4.8 or later)

Create a delegate to handle the mock invocation.

 delegate IEnumerable<SomeOtherClass> GetSomethingCallback(DateTime start, DateTime end, out bool someFlag);

In the setup use It.Ref<Bar>.IsAny for the out parameter and use the delegate in the Returns expression.

mock
    .Setup(_ => _.GetSomething(It.IsAny<DateTime>(), It.IsAny<DateTime>(), out It.Ref<bool>.IsAny))
    .Returns(new GetSomethingCallback((DateTime start, DateTime end, out bool someFlag) => {
        IEnumerable<SomeOtherClass> otherClasses = GenerateMockedData(start, end);
        //Assign something to someFlag, depending on start and end
        someFlag = true;
        return otherClasses;
    }));

The It.Ref<bool>.IsAny instructs the returns delegate to interact with the instance reference of the actual object that was passed into the mocked member.