public async Task DisposeAsync_MultipleInvokes_Idempotent(PresetScopes scope)
        {
            TestHelper.WipeStores();
            using (IsolatedStorageFile isf = GetPresetScope(scope))
            {
                IsolatedStorageFileStream isfs = isf.CreateFile("DisposeAsyncFile");
                await isfs.DisposeAsync();

                await isfs.DisposeAsync();
            }
        }
        public async Task DisposeAsync_FlushesAndCloses(PresetScopes scope)
        {
            TestHelper.WipeStores();
            using (IsolatedStorageFile isf = GetPresetScope(scope))
            {
                IsolatedStorageFileStream isfs = isf.CreateFile("DisposeAsyncFile");
                isfs.Write(new byte[100], 0, 100);
                await isfs.DisposeAsync();

                using (isfs = isf.OpenFile("DisposeAsyncFile", FileMode.Open))
                {
                    Assert.Equal(100, isfs.Length);
                }
            }
        }