public void Setup() { var enumerableConverter = new EnumerableConverter <ItemType, JsonStringEnumConverter>(); using var ms = new MemoryStream(); using (var writer = new Utf8JsonWriter(ms)) { var itemTypeList = new List <ItemType> { ItemType.Unknown, ItemType.Address }; writer.WriteStartArray(); enumerableConverter.Write(writer, itemTypeList, new JsonSerializerOptions()); writer.WriteEndArray(); } _result = System.Text.Encoding.UTF8.GetString(ms.ToArray()); }