br := NewReader(strings.NewReader("example"))
	br.WriteTo(io.Discard)
	if err := br.UnreadByte(); err == nil {
		t.Error("UnreadByte didn't fail after WriteTo")
	}
}

func TestUnreadByte(t *testing.T) {
	segments := []string{"Hello, ", "world"}
	r := NewReader(&StringReader{data: segments})
	got := ""
	want := strings.Join(segments, "")
	// Normal execution.
	for {
		b1, err := r.ReadByte()