with builtins;

[
  (replaceStrings [ "o" ] [ "a" ] "foobar")
  (replaceStrings [ "o" ] [ "" ] "foobar")
  (replaceStrings [ "oo" ] [ "u" ] "foobar")
  (replaceStrings [ "oo" "a" ] [ "a" "oo" ] "foobar")
  (replaceStrings [ "oo" "oo" ] [ "u" "i" ] "foobar")
  (replaceStrings [ "" ] [ "X" ] "abc")
  (replaceStrings [ "" ] [ "X" ] "")
  (replaceStrings [ "-" ] [ "_" ] "a-b")
  (replaceStrings [ "oo" "XX" ] [ "u" (throw "unreachable") ] "foobar")
]