let $s = " héllo 世界\n"
require ($s.trim == "héllo 世界") "Unicode trim"
require ($s.trim_start == "héllo 世界\n") "trim_start"
require ($s.trim_end == " héllo 世界") "trim_end"
require ($s.contains "世界") "contains"
require ($s.starts_with " h") "starts_with"
require ($s.ends_with "\n") "ends_with"
require (($s.replace "héllo" "hi") == " hi 世界\n") "replace"
require (("a,,b,".split ",") == ["a", "", "b", ""]) "split retains empty fields"
require ("é猫".chars == ["é", "猫"]) "chars are Unicode scalar values"
require ("".chars == []) "empty characters"
require (("".split ",") == [""]) "empty split input"
require (("é".split "") == ["", "é", ""]) "empty separator uses Unicode boundaries"
require (("aba".replace "a" "x") == "xbx") "replace every match"
require (("ab".replace "" "x") == "xaxbx") "empty replacement pattern"
require (" text ".trim == "text") "Unicode whitespace"
require ("abc".contains "") "empty substring"
require (!("abc".starts_with "bc")) "prefix negative"
require (!("abc".ends_with "ab")) "suffix negative"
require ($s == " héllo 世界\n") "string methods mutated receiver"