How to instantiate an instance of FormFile in C# without Moq?

Thanks to Hans his comment, the actual answer is:

using (var stream = File.OpenRead("placeholder.pdf"))
{
    var file = new FormFile(stream, 0, stream.Length, null, Path.GetFileName(stream.Name))
    {
        Headers = new HeaderDictionary(),
        ContentType = "application/pdf"
    };
}