int realGroupCount = pacStream.readInt();
                if ( realGroupCount != groupCount ) {
                    throw new PACDecodingException("Invalid number of groups in PAC expect" + groupCount + " have " + realGroupCount);
                }
                groups = new PacGroup[groupCount];
                for ( int i = 0; i < groupCount; i++ ) {
                    pacStream.align(4);

        if (matcher.find()) {
            if (logger.isDebugEnabled()) {
                logger.debug("Matched: {}", matcher.group());
            }
            if (matcher.groupCount() > 0) {
                return matcher.group(1);
            }
        }
        return null;
    }

    protected String replaceCredentials(final Credentials credentials, final String value) {

  }

  public void testGet_regex() {
    assertEquals(Pattern.compile("").pattern(), ArbitraryInstances.get(Pattern.class).pattern());
    assertEquals(0, ArbitraryInstances.get(MatchResult.class).groupCount());
  }

  public void testGet_usePublicConstant() {
    assertSame(WithPublicConstant.INSTANCE, ArbitraryInstances.get(WithPublicConstant.class));
  }

  public void testGet_useFirstPublicConstant() {