b.WriteString("abcdefghijklmnopqrstuvwxy") // hard
	b.WriteString("z")
	if err := b.Flush(); err != nil {
		t.Error("WriteString", err)
	}
	s := "01234567890abcdefghijklmnopqrstuvwxyz"
	if buf.String() != s {
		t.Errorf("WriteString wants %q gets %q", s, buf.String())
	}
}

func TestWriteStringStringWriter(t *testing.T) {
	const BufSize = 8
	{