mock setup with array parameter

Question

I have an issue with Mocking methods Please see below:

This is the interface

public interface IShop
{
    string CheckNames(string[] names);
}

Here is my Mock

var names = "A,B,C";
var shopMock = new Mock<IShop>(MockBehavior.Strict);
shopMock.Setup(s => s.CheckNames(names.Split(','))).Returns("GoodNames");

However when I call this method in my test, this method is failed with Moq.MockException : IShop.CheckNames(["A", "B", "C"]) invocation failed with mock behavior Strict.

var obj = shopMock.Object;
Assert.AreEqual("GoodNames", obj.CheckNames(names.Split(',')));

To make it work, I need to

var names = "A,B,C";
var shopMock = new Mock<IShop>(MockBehavior.Strict);

var nameList = names.Split(',');

shopMock.Setup(s => s.CheckNames(nameList)).Returns("GoodNames");

var obj = shopMock.Object;
Assert.AreEqual("GoodNames", obj.CheckNames(names.Split(',')));

Why I need to create nameList here to make it to work? Thanks

Pavel Anikhouski · Accepted Answer · 2020-07-10 10:13:08Z

2

It seems, that in first case test will fail, because two calls of names.Split(',') return different references for result string[] and mock setup and Assert are called with different object. You should use It.Is expression to setup mock accepting any array with A, B, C values for CheckNames in first case

var names = "A,B,C";
            
var shopMock = new Mock<IShop>(MockBehavior.Strict);
shopMock.Setup(s =>
        s.CheckNames(It.Is<string[]>(_ => _.SequenceEqual(names.Split(',', StringSplitOptions.None)))))
    .Returns("GoodNames");
var obj = shopMock.Object;
Assert.Equal("GoodNames", obj.CheckNames(names.Split(',')));

Or use the same array for Setup and Assert methods, which seems to be done in your second case (but full sample is missing)

var names = "A,B,C";
var nameList = names.Split(',');

var shopMock = new Mock<IShop>(MockBehavior.Strict);
shopMock.Setup(s => s.CheckNames(nameList)).Returns("GoodNames");
var obj = shopMock.Object;
Assert.Equal("GoodNames", obj.CheckNames(nameList));

edited Jul 10, 2020 at 10:13

answered Jul 10, 2020 at 9:51

Pavel Anikhouski

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4 Comments

Helic Over a year ago

This is the second case and it works in this way too. var names = "A,B,C"; var shopMock = new Mock<IShop>(MockBehavior.Strict); var list = names.Split(','); shopMock.Setup(s => s.CheckNames(list)).Returns("GoodNames"); var obj = shopMock.Object; Assert.AreEqual("GoodNames", obj.CheckNames(names.Split(',')));

Helic Over a year ago

Not sure why it works with Assert.AreEqual("GoodNames", obj.CheckNames(names.Split(','))); if the setup is on a different array object

Pavel Anikhouski Over a year ago

@Helic which Moq and .NET version are you using? s => s.CheckNames(names.Split(',')) will raise An expression tree may not contain a call or invocation that uses optional arguments error in my end

Helic Over a year ago

I am using Moq 4.7.99 and .net 4.6.2.

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