public async Task FileStreamingHelper_MultipartRequestHelper()
{
var contentType = $"multipart/form-data; boundary=\"{Boundary}\"";
// string contentType, Stream requestBody, AppSettings appSettings,
// ISelectorStorage selectorStorage, string headerFileName = null
var stream = MakeStream(TwoPartBody);
var storage = new FakeIStorage();
storage.CreateDirectory(_appSettings.TempFolder);
var streamSelector = new FakeSelectorStorage(storage);
await FileStreamingHelper.StreamFile(contentType, stream, _appSettings, streamSelector);
var tempPath = storage.GetAllFilesInDirectoryRecursive(_appSettings.TempFolder).FirstOrDefault();
Assert.IsTrue(tempPath?.EndsWith("a.txt"));
}