using System;

using System.Collections.Generic;

using AutoFake;

var fake = new Fake<Sut>();

var list = new List<int> { 0 };

Console.WriteLine(string.Join(", ", list));

var sut = fake.Rewrite(() => Sut.MutateArgument(list));

sut.Execute();

Console.WriteLine(string.Join(", ", list));

​

public class Sut

{

    public static void MutateArgument(List<int> list) => list.Add(1);

}