};
    for (String s : BAD_STRINGS) {
      assertThrows(IllegalArgumentException.class, () -> escapeAsString(e, s));
    }
  }

  public void testFalsePositivesForNextEscapedIndex() {
    UnicodeEscaper e =
        new UnicodeEscaper() {
          // Canonical escaper method that only escapes lower case ASCII letters.
          @Override