code: @Test public void testAppendThrowable() throws Exception {
    StringBuilder buf=new StringBuilder();
    DummyThrowableProxy tp=new DummyThrowableProxy();
    tp.setClassName("test1");
    tp.setMessage("msg1");
    StackTraceElement ste1=new StackTraceElement("c1","m1","f1",1);
    StackTraceElement ste2=new StackTraceElement("c2","m2","f2",2);
    StackTraceElementProxy[] stepArray={new StackTraceElementProxy(ste1),new StackTraceElementProxy(ste2)};
    tp.setStackTraceElementProxyArray(stepArray);
    DefaultThrowableRenderer renderer=(DefaultThrowableRenderer)layout.getThrowableRenderer();
    renderer.render(buf,tp);
    System.out.println(buf.toString());
    String[] result=buf.toString().split(CoreConstants.LINE_SEPARATOR);
    System.out.println(result[0]);
    assertEquals("test1: msg1",result[0]);
    assertEquals(DefaultThrowableRenderer.TRACE_PREFIX + "at c1.m1(f1:1)",result[1]);
  }
  