Capture multiple arguments with NSubstitute

Question

I am using NSubstitute to write a unit test, and am trying to capture multiple method arguments passed in a method call.

I understand that I can capture a single argument using the Arg.Do<T>() matcher by doing something like this for SomeMethod which only accepts one parameter:

TArg? receivedArg = null;
SomeClass.SomeMethod(Arg.Do<TArg>(arg => receivedArg = arg));

However in my case, SomeMethod multiple arguments, and I want to capture all of them in each call.

Answer 1

Check the Callbacks, void calls and When..Do topic.

You can hook an Action<CallInfo> callback to your SomeMethod method; its CallInfo argument has an Args method that returns all passed arguments as an object[] array. There's also an ArgAt<T>(int position) method for strong typed access to a specific argument.

---

object[] receivedArgs;
int receivedArg1;
string receivedArg2;
bool receivedArg3;

var dependency = Substitute.For<IDependency>();

dependency
    .When(o => o.SomeMethod(Arg.Any<int>(), Arg.Any<string>(), Arg.Any<bool>()))
    .Do(callInfo =>
    {
        receivedArgs = callInfo.Args();

        receivedArg1 = callInfo.ArgAt<int>(0);
        receivedArg2 = callInfo.ArgAt<string>(1);
        receivedArg3 = callInfo.ArgAt<bool>(2);
    });

var myClass = new MyClass(dependency);
myClass.Run();

// Check received args here.

public interface IDependency
{
    void SomeMethod(int arg1, string arg2, bool arg3);
}

public class MyClass
{
    private readonly IDependency _dependency;

    public MyClass(IDependency myClass)
    {
        _dependency = myClass;
    }

    public void Run()
    {
        _dependency.SomeMethod(123, "foo", false);
    }
}