assertUnicodeEscaping(e, "%F4%8F%BF%BF", '\uDBFF', '\uDFFF');

    assertEquals("", e.escape(""));
    assertEquals("safestring", e.escape("safestring"));
    assertEquals("embedded%00null", e.escape("embedded\0null"));
    assertEquals("max%EF%BF%BFchar", e.escape("max\uffffchar"));
  }

  // Helper to assert common expected behaviour of uri escapers.
  static void assertBasicUrlEscaper(UnicodeEscaper e) {

    Escaper escaper = Escapers.nullEscaper();
    EscaperAsserts.assertBasic(escaper);
    String s = "\0\n\t\\az09~\uD800\uDC00\uFFFF";
    assertEquals("null escaper should have no effect", s, escaper.escape(s));
  }

  public void testBuilderInitialStateNoReplacement() {
    // Unsafe characters aren't modified by default (unsafeReplacement == null).

    assertUnicodeEscaping(e, "%F4%8F%BF%BF", '\uDBFF', '\uDFFF');

    assertEquals("", e.escape(""));
    assertEquals("safestring", e.escape("safestring"));
    assertEquals("embedded%00null", e.escape("embedded\0null"));
    assertEquals("max%EF%BF%BFchar", e.escape("max\uffffchar"));
  }

  // Helper to assert common expected behaviour of uri escapers.
  static void assertBasicUrlEscaper(UnicodeEscaper e) {

          || c < safeMinChar) {
        return escapeSlow(s, i);
      }
    }
    return s;
  }

  /**
   * Escapes a single Unicode code point using the replacement array and safe range values. If the
   * given character does not have an explicit replacement and lies outside the safe range then
   * {@link #escapeUnsafe} is called.
   *

      "\0abyz\u0080\u0100\u0800\u1000ABYZ\uffff" + SMALLEST_SURROGATE + "0189" + LARGEST_SURROGATE;

  // Escapes nothing
  private static final UnicodeEscaper NOP_ESCAPER =
      new UnicodeEscaper() {
        @Override
        protected char @Nullable [] escape(int c) {
          return null;
        }
      };

  // Escapes everything except [a-zA-Z0-9]
  private static final UnicodeEscaper SIMPLE_ESCAPER =

      "\0abyz\u0080\u0100\u0800\u1000ABYZ\uffff" + SMALLEST_SURROGATE + "0189" + LARGEST_SURROGATE;

  // Escapes nothing
  private static final UnicodeEscaper NOP_ESCAPER =
      new UnicodeEscaper() {
        @Override
        protected char @Nullable [] escape(int c) {
          return null;
        }
      };

  // Escapes everything except [a-zA-Z0-9]
  private static final UnicodeEscaper SIMPLE_ESCAPER =

   *
   * @param replacements a map of characters to their escaped representations
   */
  public static ArrayBasedEscaperMap create(Map<Character, String> replacements) {
    return new ArrayBasedEscaperMap(createReplacementArray(replacements));
  }

  // The underlying replacement array we can share between multiple escaper
  // instances.
  private final char[][] replacementArray;

     * is that in JavaScript, a single quote must be escaped.</p>
     *
     * <p>Example:</p>
     * <pre>
     * input string: He didn't say, "Stop!"
     * output string: He didn't say, \"Stop!\"
     * </pre>
     *
     *
     * @param str  String to escape values in, may be null
     * @return String with escaped values, <code>null</code> if null string input
     */

    UnicodeEscaper e = (UnicodeEscaper) urlFormParameterEscaper();
    // Verify that these are the same escaper (as documented)
    assertSame(e, urlFormParameterEscaper());
    assertBasicUrlEscaper(e);

    /*
     * Specified as safe by RFC 2396 but not by java.net.URLEncoder. These tests will start failing
     * when the escaper is made compliant with RFC 2396, but that's a good thing (just change them
     * to assertUnescaped).
     */

    UnicodeEscaper e = (UnicodeEscaper) urlFormParameterEscaper();
    // Verify that these are the same escaper (as documented)
    assertSame(e, urlFormParameterEscaper());
    assertBasicUrlEscaper(e);

    /*
     * Specified as safe by RFC 2396 but not by java.net.URLEncoder. These tests will start failing
     * when the escaper is made compliant with RFC 2396, but that's a good thing (just change them
     * to assertUnescaped).
     */