@Test
public void testClear() throws Exception {

    DubboAppender.doStart();
    DubboAppender appender = new DubboAppender();
    appender.append(event);
      assertThat(DubboAppender.logList, hasSize(1));
    DubboAppender.clear();
      assertThat(DubboAppender.logList, hasSize(0));
}