code: @Test public void testInvalidInput(){
    HttpMessage message=new TestHttpMessage();
    try {
      message.setParams(null);
      Assert.fail("IllegalArgumentException should have been thrown");
    }
   catch (  IllegalArgumentException ex) {
    }
    try {
      message.addHeader(null,null);
      Assert.fail("IllegalArgumentException should have been thrown");
    }
   catch (  IllegalArgumentException ex) {
    }
    try {
      message.setHeader(null,null);
      Assert.fail("IllegalArgumentException should have been thrown");
    }
   catch (  IllegalArgumentException ex) {
    }
  }
  