code: @Test public void testInvalidInput() throws Exception {
    HttpRequestHandlerRegistry registry=new HttpRequestHandlerRegistry();
    try {
      registry.register(null,null);
      Assert.fail("IllegalArgumentException should have been thrown");
    }
   catch (  IllegalArgumentException ex) {
    }
    try {
      registry.register("",null);
      Assert.fail("IllegalArgumentException should have been thrown");
    }
   catch (  IllegalArgumentException ex) {
    }
    registry.unregister(null);
    try {
      registry.setHandlers(null);
      Assert.fail("IllegalArgumentException should have been thrown");
    }
   catch (  IllegalArgumentException ex) {
    }
    try {
      registry.lookup(null);
      Assert.fail("IllegalArgumentException should have been thrown");
    }
   catch (  IllegalArgumentException ex) {
    }
  }
  