public async Task WriteFileBytesAppend() { var imageBytes = System.IO.File.ReadAllBytes(BinaryTestFilePath); TestFileContext.CreateBinaryFile("test.png", new byte[] { 137, 80, 78, 71, 13, 10, 26, 10 }); // empty png var result = await File.WriteBytes( new WriteBytesInput() { ContentBytes = imageBytes, Path = Path.Combine(TestFileContext.RootPath, "test.png") }, new WriteBytesOption() { WriteBehaviour = WriteBehaviour.Append }); var fileContentBytes = System.IO.File.ReadAllBytes(result.Path); Assert.Equal(8 + imageBytes.Length, fileContentBytes.Length); }