Assigning out/ref parameters in Moq

Question

Is it possible to assign an out/ref parameter using Moq (3.0+)?

I've looked at using Callback(), but Action<> does not support ref parameters because it's based on generics. I'd also preferably like to put a constraint (It.Is) on the input of the ref parameter, though I can do that in the callback.

I know that Rhino Mocks supports this functionality, but the project I'm working on is already using Moq.

Answer 1

For 'out', the following seems to work for me.

public interface IService {     void DoSomething(out string a); }  [TestMethod] public void Test() {     var service = new Mock<IService>();     var expectedValue = "value";     service.Setup(s => s.DoSomething(out expectedValue));      string actualValue;     service.Object.DoSomething(out actualValue);     Assert.AreEqual(expectedValue, actualValue); } 

I'm guessing that Moq looks at the value of 'expectedValue' when you call Setup and remembers it.

For ref, I'm looking for an answer also.

I found the following QuickStart guide useful: https://github.com/Moq/moq4/wiki/Quickstart

Answer 2

Moq version 4.8 (or later) has much improved support for by-ref parameters:

public interface IGobbler {     bool Gobble(ref int amount); }  delegate void GobbleCallback(ref int amount);     // needed for Callback delegate bool GobbleReturns(ref int amount);      // needed for Returns  var mock = new Mock<IGobbler>(); mock.Setup(m => m.Gobble(ref It.Ref<int>.IsAny))  // match any value passed by-ref     .Callback(new GobbleCallback((ref int amount) =>      {          if (amount > 0)          {              Console.WriteLine("Gobbling...");              amount -= 1;          }      }))     .Returns(new GobbleReturns((ref int amount) => amount > 0));  int a = 5; bool gobbleSomeMore = true; while (gobbleSomeMore) {     gobbleSomeMore = mock.Object.Gobble(ref a); } 

The same pattern works for out parameters.

It.Ref<T>.IsAny also works for C# 7 in parameters (since they are also by-ref).