Hi I have error on final StringWriter stringWriter = new StringWriter(); new MockUp<Logger>() { @Mock void error(String format, Object... arguments) { boolean isFirst = true; for (Object arg : arguments) { if (!isFirst) { stringWriter.append("#"); } stringWriter.append(String.valueOf(arg)); isFirst = false; } } }; when i use org.glassfish.metro.webservices-rt 2.4.5 regards