[]byte("\xc0a\xc0"),
		[]byte("\xc0a\xc0cd"),
		[]byte("ab\xc0a\xc0")},
	{not(isValidRune), "\xc0a\xc0",
		[]byte("a"),
		[]byte("a\xc0"),
		[]byte("\xc0a")},
	// The nils returned by TrimLeftFunc are odd behavior, but we need
	// to preserve backwards compatibility.
	{isSpace, "",
		nil,
		nil,
		[]byte("")},
	{isSpace, " ",
		nil,
		nil,
		[]byte("")},
}