public async Task Can_append_to_csv() { List <MiabData> miabData; using (var fs = new FileStream("output.json", FileMode.Open, FileAccess.Read)) { miabData = await fs.GetMiabData().ConfigureAwait(false); } using (var fs = new FileStream("partition-data.csv", FileMode.Append, FileAccess.Write)) { fs.AppendToCSV(miabData); } }