program.cs

using BenchmarkDotNet.Attributes;
using BenchmarkDotNet.Running;

public class Program
{
    public static void Main(string[] args)
    {
        var summary= BenchmarkRunner.Run<ListCapacityPerformance>();
    }
}

[MemoryDiagnoser]
public class ListCapacityPerformance
{
    [Params(20, 80, 300, 800)]
    public int capacity;

    [Benchmark]
    public List<int> DynamicCapacity()
    {
        List<int> squidList = new List<int>();
        for (int i = 0; i < capacity; i++)
        {            
            squidList.Add(i);
        }
        return squidList;
    }

    [Benchmark]
    public List<int> SetCapacity()
    {
        List<int> squidList = new List<int>(capacity);
        for (int i = 0; i < capacity; i++)
        {
            squidList.Add(i);
        }
        return squidList;
    }
}