@Override
      protected char @Nullable [] escape(char c) {
        return replacementMap.get(c);
      }
    };
  }

  // A trivial non-optimized escaper for testing.
  static UnicodeEscaper createSimpleUnicodeEscaper(ImmutableMap<Integer, char[]> replacementMap) {
    return new UnicodeEscaper() {
      @Override
      protected char @Nullable [] escape(int cp) {
        return replacementMap.get(cp);
      }
    };