Mocked out parameter value is stuck inspite of calling CallRouter.Clear(ClearOptions.All)

[davidnemeti]

Describe the bug

After mocking an out parameter value either either with Returns or with When-Do, the mocked out parameter value is stuck inspite of calling CallRouter.Clear(ClearOptions.All).

I believe this might be happen because when the out parameter value is being set, then it goes directly into the Call._arguments, where it stays forever despite the CallRouter.Clear(ClearOptions.All) call, until another Returns or When-Do sets the out parameter value to something else.

To Reproduce

void Main()
{
    var foo = Substitute.For<IFoo>();

    int number1, number2;

    Console.WriteLine("Empty substitute");

    foo.Baz(out number1);
    foo.Bar(out number2);

    Console.WriteLine(number1);
    Console.WriteLine(number2);

    foo
        .Baz(out Arg.Any<int>())
        .Returns(callInfo =>
        {
            Console.WriteLine("Inside 'Returns'");
            callInfo[0] = 5;
            return 21;
        });

    foo
        .When(x => x.Bar(out Arg.Any<int>()))
        .Do(callInfo =>
        {
            Console.WriteLine("Inside 'Do'");
            callInfo[0] = 8;
        });

    Console.WriteLine();
    Console.WriteLine("Mocked substitute");

    foo.Baz(out number1);
    foo.Bar(out number2);

    Console.WriteLine(number1);
    Console.WriteLine(number2);

    var callRouter = SubstitutionContext.Current.GetCallRouterFor(foo);
    callRouter.Clear(ClearOptions.All);

    Console.WriteLine();
    Console.WriteLine("Cleared substitute");

    foo.Baz(out number1);
    foo.Bar(out number2);

    Console.WriteLine(number1);
    Console.WriteLine(number2);
}

public interface IFoo
{
    void Bar(out int number);
    int Baz(out int number);
}

The above code writes this to the console:

Empty substitute
0
0

Mocked substitute
Inside 'Returns'
Inside 'Do'
5
8

Cleared substitute
5
8

Expected behaviour

The above code should write this to the console:

Empty substitute
0
0

Mocked substitute
Inside 'Returns'
Inside 'Do'
5
8

Cleared substitute
0
0

Environment

• NSubstitute version: 4.2.1
• Platform: .NET Framework 4.8 on Windows

[davidnemeti]

Nevermind, NSubstitute works correctly from this perspective. I was wrong, the out parameter is not stuck. See the following example:

void Main()
{
    var foo = Substitute.For<IFoo>();

    int number1, number2;

    number1 = 11;
    number2 = 22;
    Console.WriteLine("Empty substitute");

    foo.Baz(out number1);
    foo.Bar(out number2);

    Console.WriteLine(number1);
    Console.WriteLine(number2);

    foo
        .Baz(out Arg.Any<int>())
        .Returns(callInfo =>
        {
            Console.WriteLine("Inside 'Returns'");
            callInfo[0] = 5;
            return 21;
        });

    foo
        .When(x => x.Bar(out Arg.Any<int>()))
        .Do(callInfo =>
        {
            Console.WriteLine("Inside 'Do'");
            callInfo[0] = 8;
        });

    number1 = 33;
    number2 = 44;
    Console.WriteLine();
    Console.WriteLine("Mocked substitute");

    foo.Baz(out number1);
    foo.Bar(out number2);

    Console.WriteLine(number1);
    Console.WriteLine(number2);

    var callRouter = SubstitutionContext.Current.GetCallRouterFor(foo);
    callRouter.Clear(ClearOptions.All);

    Console.WriteLine();
    Console.WriteLine("Cleared substitute");

    foo.Baz(out number1);
    foo.Bar(out number2);

    number1 = 55;
    number2 = 66;
    Console.WriteLine(number1);
    Console.WriteLine(number2);
}

public interface IFoo
{
    void Bar(out int number);
    int Baz(out int number);
}

The output is:

Empty substitute
11
22

Mocked substitute
Inside 'Returns'
Inside 'Do'
5
8

Cleared substitute
55
66

We can see that the "Empty substitute" and the "Cleared substitute" cases work the same: they do not change the value of the out parameter at all.

Now, another topic could be whether this is a good thing or not; but this deserves another issue: #590

[dtchepak]

Thanks for following this up. 👍

Quick aside in case you hadn't seen it: you can import NSubstitute.ClearExtensions to run clear without having to fetch the call router (same code, just a bit shorter).