for i, r := range res {
			e := exp[i]
			if r != e {
				t.Errorf("test %q, lookup %q, result %d: expected index %d; got %d", tc.name, s, i, e, r)
			}
		}
	}
}

func testFindAllIndex(t *testing.T, tc *testCase, x *Index, rx *regexp.Regexp, n int) {
	res := x.FindAllIndex(rx, n)
	exp := rx.FindAllStringIndex(tc.source, n)

	// check that the lengths match
	if len(res) != len(exp) {