Using multiple indexers with Moq

Question

I have been trying to use Moq to fake an object set (and get) with multiple indexers. I have previously been using Moq with single indexers for quite some time, but it doesn't seem to be working using multiple indexers. I am aware from my research that Moq can have a problem using It.IsAny<> for indexer parameters, but I have also tried the following code with specific parameters (like mock[1, "BlockItem"]) Here is my code:

m_storageAccessor.SetupSet(
mock => mock[It.IsAny<int>(), It.IsAny<string>()] = It.IsAny<object>()).Callback(
                (int i, string s, object o) =>
                       {
                           m_storageAccessor.SetupGet(
                               mock => mock[i, s]).Returns(
                                   () => { return o; });
                       });

This generates the following exception, again, no matter what parameters I give the indexer function in SetupSet().

Initialization method UnitTest.BonusHandlerTest.MyTestInitialize threw exception. System.ArgumentNullException: System.ArgumentNullException: Value cannot be null. Parameter name: arguments.

System.Linq.Expressions.Expression.ValidateArgumentTypes(MethodInfo method, ReadOnlyCollection1& arguments) System.Linq.Expressions.Expression.ValidateCallArgs(Expression instance, MethodInfo method, ReadOnlyCollection1& arguments) System.Linq.Expressions.Expression.Call(Expression instance, MethodInfo method, IEnumerable1 arguments) System.Linq.Expressions.Expression.Call(Expression instance, MethodInfo method, Expression[] arguments) TCall](Mock1 mock, Action1 setterExpression, Func5 callFactory) b__25() Moq.PexProtector.Invoke[T](Func1 function) Moq.Mock.SetupSet[T](Mock1 mock, Action1 setterExpression, Func1 condition) SetupSet(Action`1 setterExpression) UnitTest.BonusHandlerTest.SetupPersistence() in C:\perforce\dev\KHIRST_Client12.BonusHandler\Client12\Gaming\BonusHandler\UnitTest\BonusHandlerTest.cs: line 868 UnitTest.BonusHandlerTest.MyTestInitialize() in C:\perforce\dev\KHIRST_Client12.BonusHandler\Client12\Gaming\BonusHandler\UnitTest\BonusHandlerTest.cs: line 100

It almost seems like, based on what I have tried, that Moq is unable to do indexers with multiple parameters. Anyone have any ideas? The interwebs haven't been much help.

Erik Dietrich Erik Dietrich · Accepted Answer · 2011-10-24T17:21:14

For what it's worth, I set this scenario up and there were no exceptions:

        var myStub = new Mock<Foo>();
        myStub.SetupSet(foo => foo[12, "asdf"] = null).Callback((int i, string s, object o) => myStub.SetupGet(foo => foo[i, s]).Returns(o));

It appears that it doesn't just like the It.IsAny<> for the parameters to the indexer, but also to the set value. I've never tried to do this in my testing, but this seems like a current limitation of the tool to me.

Using multiple indexers with Moq

1 Answers