b1[j] = 'x'
			pos := IndexByte(b1, 'x')
			if pos != j {
				t.Errorf("IndexByte(%q, 'x') = %v", b1, pos)
			}
			b1[j] = 0
			pos = IndexByte(b1, 'x')
			if pos != -1 {
				t.Errorf("IndexByte(%q, 'x') = %v", b1, pos)
			}
		}
		// different end alignments
		b1 = b[:i]
		for j := 0; j < len(b1); j++ {
			b1[j] = 'x'
			pos := IndexByte(b1, 'x')
			if pos != j {