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
	{
		tw := &teststringwriter{}
		b := NewWriterSize(tw, BufSize)
		b.WriteString("1234")
		tw.check(t, "", "")
		b.WriteString("56789012")   // longer than BufSize