@Override
    public void beforeTestExecution(ExtensionContext extensionContext) {
        StringLayout layout = PatternLayout.newBuilder().withPattern(PATTERN).build();
        appender = WriterAppender.newBuilder()
            .setTarget(outContent)
            .setLayout(layout)
            .setName(APPENDER_NAME).build();
        appender.start();
        for (Logger logger : loggers) {
            logger.addAppender(appender);
        }
    }
Logged messages contains level and message only.
This allows us to test that level and message are set.
analyzer/src/test/java/nl/basjes/parse/useragent/utils/LogMessagesScraper.java