* characters.
 *
 * <p>As there are important reasons, including potential security issues, to handle Unicode
 * correctly if you are considering implementing a new escaper you should favor using UnicodeEscaper
 * wherever possible.
 *
 * <p>A {@code UnicodeEscaper} instance is required to be stateless, and safe when used concurrently
 * by multiple threads.
 *
 * <p>Popular escapers are defined as constants in classes like {@link

 * characters.
 *
 * <p>As there are important reasons, including potential security issues, to handle Unicode
 * correctly if you are considering implementing a new escaper you should favor using UnicodeEscaper
 * wherever possible.
 *
 * <p>A {@code UnicodeEscaper} instance is required to be stateless, and safe when used concurrently
 * by multiple threads.
 *
 * <p>Popular escapers are defined as constants in classes like {@link

    assertEquals("foo%40bar.com", e.escape("******@****.***"));
  }

  public void testUrlPathSegmentEscaper() {
    UnicodeEscaper e = (UnicodeEscaper) urlPathSegmentEscaper();
    assertPathEscaper(e);
    assertUnescaped(e, '+');
  }

  public void testUrlFragmentEscaper() {
    UnicodeEscaper e = (UnicodeEscaper) urlFragmentEscaper();
    assertUnescaped(e, '+');
    assertUnescaped(e, '/');
    assertUnescaped(e, '?');

  // 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 =
      new UnicodeEscaper() {
        @Override
        protected char @Nullable [] escape(int cp) {

  // 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 =
      new UnicodeEscaper() {
        @Override
        protected char @Nullable [] escape(int cp) {

  }

  /** Tests the various ways that the space character can be handled */
  public void testPlusForSpace() {
    UnicodeEscaper basicEscaper = new PercentEscaper("", false);
    UnicodeEscaper plusForSpaceEscaper = new PercentEscaper("", true);
    UnicodeEscaper spaceEscaper = new PercentEscaper(" ", false);

    assertEquals("string%20with%20spaces", basicEscaper.escape("string with spaces"));

    assertEquals("foo%40bar.com", e.escape("******@****.***"));
  }

  public void testUrlPathSegmentEscaper() {
    UnicodeEscaper e = (UnicodeEscaper) urlPathSegmentEscaper();
    assertPathEscaper(e);
    assertUnescaped(e, '+');
  }

  public void testUrlFragmentEscaper() {
    UnicodeEscaper e = (UnicodeEscaper) urlFragmentEscaper();
    assertUnescaped(e, '+');
    assertUnescaped(e, '/');
    assertUnescaped(e, '?');

  }

  // Helper to assert common expected behaviour of uri escapers.
  static void assertBasicUrlEscaper(UnicodeEscaper e) {
    assertBasicUrlEscaperExceptPercent(e);
    // The escape character must always be escaped
    assertEscaping(e, "%25", '%');
  }

  static void assertPathEscaper(UnicodeEscaper e) {
    assertBasicUrlEscaper(e);

    assertUnescaped(e, '!');
    assertUnescaped(e, '\'');

   * {@code EscaperAsserts} class; production users of {@link UnicodeEscaper} should limit
   * themselves to its public interface.
   *
   * @param cp the Unicode code point to escape if necessary
   * @return the replacement string, or {@code null} if no escaping was needed
   */
  public static @Nullable String computeReplacement(UnicodeEscaper escaper, int cp) {
    return stringOrNull(escaper.escape(cp));
  }

  }

  /** Tests the various ways that the space character can be handled */
  public void testPlusForSpace() {
    UnicodeEscaper basicEscaper = new PercentEscaper("", false);
    UnicodeEscaper plusForSpaceEscaper = new PercentEscaper("", true);
    UnicodeEscaper spaceEscaper = new PercentEscaper(" ", false);

    assertEquals("string%20with%20spaces", basicEscaper.escape("string with spaces"));