}

	writer = WriteOnClose(io.Discard)
	writer.Close()
	if !writer.HasWritten() {
		t.Error("WriteOnCloser must be marked as HasWritten")
	}
}

// Test for AppendFile.
func TestAppendFile(t *testing.T) {
	f, err := os.CreateTemp("", "")
	if err != nil {
		t.Fatal(err)
	}
	name1 := f.Name()
	defer os.Remove(name1)
	f.WriteString("aaaaaaaaaa")
	f.Close()

  std::unique_ptr<WritableFile> new_file;
  status = env_->NewWritableFile(new_path, &new_file);
  EXPECT_PRED2(UnimplementedOrReturnsCode, status, Code::FAILED_PRECONDITION);
}

TEST_P(ModularFileSystemTest, TestAppendFile) {
  const std::string filepath = GetURIForPath("a_file");
  std::unique_ptr<WritableFile> new_file;
  Status status = env_->NewAppendableFile(filepath, &new_file);