code: @Test public void testRegisterUnregister() throws Exception {
    HttpRequestHandler h1=new DummyHttpRequestHandler();
    HttpRequestHandler h2=new DummyHttpRequestHandler();
    HttpRequestHandler h3=new DummyHttpRequestHandler();
    HttpRequestHandlerRegistry registry=new HttpRequestHandlerRegistry();
    registry.register("/h1",h1);
    registry.register("/h2",h2);
    registry.register("/h3",h3);
    Map<String,HttpRequestHandler> handlers=registry.getHandlers();
    Assert.assertEquals(3,handlers.size());
    HttpRequestHandler h;
    h=registry.lookup("/h1");
    Assert.assertNotNull(h);
    Assert.assertTrue(h1 == h);
    h=registry.lookup("/h2");
    Assert.assertNotNull(h);
    Assert.assertTrue(h2 == h);
    h=registry.lookup("/h3");
    Assert.assertNotNull(h);
    Assert.assertTrue(h3 == h);
    registry.unregister("/h1");
    h=registry.lookup("/h1");
    Assert.assertNull(h);
    handlers=registry.getHandlers();
    Assert.assertEquals(2,handlers.size());
    Map<String,HttpRequestHandler> map=new HashMap<String,HttpRequestHandler>();
    map.put("/a1",h1);
    map.put("/a2",h2);
    map.put("/a3",h3);
    registry.setHandlers(map);
    handlers=registry.getHandlers();
    Assert.assertEquals(3,handlers.size());
    h=registry.lookup("/h2");
    Assert.assertNull(h);
    h=registry.lookup("/h3");
    Assert.assertNull(h);
    h=registry.lookup("/a1");
    Assert.assertNotNull(h);
    Assert.assertTrue(h1 == h);
  }
  