MOQ - setting up a method based on argument values (multiple arguments)

Question

I have an interface defined as

interface IMath
{
 AddNumbersBetween(int lowerVal, int upperVal);
}

I can setup a basic Moq for the above as follows:

Mock<IMath> mock = new Mock<IMath>();    
mock.Setup(m => m.AddNumbersBetween(It.IsAny<int>(), It.IsAny<int>()));

call it

mock.Object.AddNumbersBetween(1,4);

and then verify that it was called

mock.Verify(m => m.AddNumbersBetween(1,4), Times.AtleastOnce());

I cant figure out how to setup the method AddNumbersBetween such that if the upperVal is lower than the lowerVal an exception is thrown

mock.Object.AddNumbersBetween(4,1);//should throw an exception

Essentially looking for something like:

mock.Setup(foo => foo.AddNumbersBetween("arg1 is higher than arg2")).Throws<ArgumentException>();

I would recommend simply implementing the exception-throwing logic with a Callback, as that gives you full access to both parameters. As far as I know, the parameter matching clauses can only perform logic based on a single parameter. — Dan Bryant, Nov 02 '10 at 19:07

score 167 · Accepted Answer · edited Dec 11 '18 at 10:08

167

I know this is a year old, but I found a way to use multiple parameters with the latest version of Moq at least:

mock.Setup(x => x.Method(It.IsAny<int>(), It.IsAny<int>()))
    .Returns<int, int>((a, b) => a < b);

edited Dec 11 '18 at 10:08

Peter

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answered Dec 01 '11 at 19:35

Gustyn

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@NightOwl888 Nope...When you have only a return sentence, you don't need to. – S Itzik Nov 11 '20 at 09:50
1

Apparently there is no similar `.ReturnsAsync<>`? Seems like a gap. – Patrick Szalapski Oct 10 '22 at 13:47

srodriguez · Answer 2 · 2010-11-03T08:54:38.043

For single argument methods, the cleanest way would be:

mock.Setup(foo => foo.Submit(IsLarge())).Throws<ArgumentException>();
...
public string IsLarge() 
{ 
  return Match<string>.Create(s => !String.IsNullOrEmpty(s) && s.Length > 100);
}

This can't be applied if the method has several arguments. There is still a 'workaround' that could be used, that mimics what you want to achieve:

/// <summary>
/// Tests if a moq can send an exception with argument checking
///</summary>
[TestMethod]
public void TestException()
{
    Mock<IMath> mock = new Mock<IMath>();
    mock.Setup(m => m.AddNumbersBetween(It.IsAny<int>(), It.IsAny<int>()));

    mock.Setup(foo => foo.AddNumbersBetween(It.IsAny<int>(), It.IsAny<int>()))
        .Callback<int, int>((i, j) => CheckArgs(i, j));

    try
    {
        mock.Object.AddNumbersBetween(1, 2);
    }
    catch (Exception ex)
    {
        // Will not enter
        Console.WriteLine("Exception raised: {0}", ex);
    }
    try
    {
        mock.Object.AddNumbersBetween(2, 1);
    }
    catch (Exception ex)
    {
        // Will enter here, exception raised
        Console.WriteLine("Exception raised: {0}", ex);
    }
}

private bool CheckArgs(int i, int j)
{
    if( i > j)
        throw new ArgumentException();
    return true;
}

This works only on a single parameter and not multiple parameters — Raj Rao, Nov 02 '10 at 20:48
My bad... there is another way of handling this, with a callback that will throw the exception if the arguments don't pass your validation. I've edited my answer with that method — srodriguez, Nov 03 '10 at 08:58

MOQ - setting up a method based on argument values (multiple arguments)

2 Answers2