{"a☺b☻c☹d\xe2\x98�\xff�\xed\xa0\x80", utf8.MaxRune + 1, -1},

		// Test the cutover to bytealg.Index when it is triggered in
		// the middle of rune that contains consecutive runs of equal bytes.
		{"aaaaaKKKK\U000bc104", '\U000bc104', 17}, // cutover: (n + 16) / 8
		{"aaaaaKKKK鄄", '鄄', 17},
		{"aaKKKKKa\U000bc104", '\U000bc104', 18}, // cutover: 4 + n>>4
		{"aaKKKKKa鄄", '鄄', 18},
	}
	for _, tt := range tests {

			// Give up on IndexByte, it isn't skipping ahead
			// far enough to be better than Rabin-Karp.
			// Experiments (using IndexPeriodic) suggest
			// the cutover is about 16 byte skips.
			// TODO: if large prefixes of sep are matching
			// we should cutover at even larger average skips,
			// because Equal becomes that much more expensive.
			// This code does not take that effect into account.