assert_eq("banana".find("na"), 2)
assert_eq("banana".find("na", 3, 1), -1)
assert_eq("aaaa".find("a", 1, 1), -1)
assert_eq("aaaa".find("a", 1, 50), 1)
assert_eq("aaaa".find("aaaaa"), -1)
assert_eq("abababa".find("ab", 1), 2)
assert_eq("abababa".find("ab", 0), 0)
assert_eq("abababa".find("ab", -1), -1)
assert_eq("abababa".find("ab", -2), -1)
assert_eq("abababa".find("ab", -3), 4)
assert_eq("abababa".find("ab", 0, 1), -1)
assert_eq("abababa".find("ab", 0, 2), 0)
assert_eq("abababa".find("ab", -1000), 0)
assert_eq("abababa".find("ab", 1000), -1)
assert_eq("".find("a", 1), -1)

assert_eq("banana".rfind("na"), 4)
assert_eq("banana".rfind("na", 3, 1), -1)
assert_eq("aaaa".rfind("a", 1, 1), -1)
assert_eq("aaaa".rfind("a", 1, 50), 3)
assert_eq("aaaa".rfind("aaaaa"), -1)
assert_eq("abababa".rfind("ab", 1), 4)
assert_eq("abababa".rfind("ab", 0), 4)
assert_eq("abababa".rfind("ab", -1), -1)
assert_eq("abababa".rfind("ab", -2), -1)
assert_eq("abababa".rfind("ab", -3), 4)
assert_eq("abababa".rfind("ab", 0, 1), -1)
assert_eq("abababa".rfind("ab", 0, 2), 0)
assert_eq("abababa".rfind("ab", -1000), 4)
assert_eq("abababa".rfind("ab", 1000), -1)
assert_eq("".rfind("a", 1), -1)