how to mock ReadOnlySpan param?

[ali50m]

I have a generic method like below,

public interface IItemsIndexFetchService
{
    T GetItemByIndex<T>(ReadOnlySpan<T> items, int index);
}

But I have no idea about how to mock the ReadOnlySpan parameter for this method. Could you helpl me out? Thanks!

 _mocker
    .GetMock<IItemsIndexFetchService>()
    .Setup(x => x.GetItemByIndex(It.IsAny<[HOW]>(), It.IsAny<int>()))
    .Returns( [HOW] );