Mocking foreach loop with Moq

Question

I want to loop throug a XmlNodeList. How do you mock a XmlNodeList in Moq, so you can loop through it like in a foreach loop:

 foreach (XmlNode xmlNode in nodes) { //Do something with node }

I have tried to set up via a the SetupSequence method, but I haven't been able to create the desired mock.

It's a bit difficult to understand what you're trying to achieve through this test, however you might want to consider doing an integration test here rather than a unit test, providing a string representation of your xml and testing your loop on real data. — nieve
– nieve, Commented Oct 31, 2012 at 16:14
You are right about me being in that grey area, where you can discuss the value of a true unit test. However, this could be usefull in other not so grey areas. Won't I run into the same problem with all foreach loops? — Morten
– Morten, Commented Oct 31, 2012 at 16:21
The difference is what you're looping on- an xml document is more complex than any other collection and therefore might not be the best candidate for a simple unit test, obviously depending on what you are trying to test exactly. Also, this question might be a good indicator for you to rethink your design? Just a thought. — nieve
– nieve, Commented Oct 31, 2012 at 16:26
@nieve Thanks for setting me straight on Moq's capabilities, that was totally news to me. More helpfully, doesn't foreach implicitly call the GetEnumerator method of whatever is being foreached? Perhaps mocking that method could get you what you're looking for. — tmesser
– tmesser, Commented Oct 31, 2012 at 16:28
The whole idea of mocking something is saving us time and more importantly 'decoupling' our test from other dependencies. In this case, even though we don't have the whole code (and therefore it's rather difficult to say), it seems like you'd anyway end up doing the exact job by 'setting up' the mocked object or setting up the real one, hence my recommendation. — nieve
– nieve, Commented Oct 31, 2012 at 16:34

Jean-David Lanz · Accepted Answer · 2024-03-14 14:34:26Z

The foreach calls GetEnumerator under the hood and that's what you need to mock:

var xmlNodesMock = new Mock<XmlNodeList>(); xmlNodesMock .Setup(l => l.GetEnumerator()) .Returns(new XmlNode[] { /* values go here */ }.GetEnumerator());

Naturally you need to initialize XmlNode array in Returns method with actual values. Keep in mind that mocked list has to be injectable to the tested method, so that you can replace actual implementation.

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