t.Errorf("DeadlineWriter should succeed but failed with %s", err)
	}
	if n != 4 {
		t.Errorf("DeadlineWriter should succeed but should have only written 4 bytes, but returned %d instead", n)
	}
}

func TestCloseOnWriter(t *testing.T) {
	writer := WriteOnClose(io.Discard)
	if writer.HasWritten() {
		t.Error("WriteOnCloser must not be marked as HasWritten")
	}
	writer.Write(nil)
	if !writer.HasWritten() {