code: @Test public void testContextOperations(){
    HttpContext parentContext=new SyncBasicHttpContext(null);
    HttpContext currentContext=new SyncBasicHttpContext(parentContext);
    parentContext.setAttribute("param1","1");
    parentContext.setAttribute("param2","2");
    currentContext.setAttribute("param3","3");
    currentContext.setAttribute("param2","4");
    Assert.assertEquals("1",parentContext.getAttribute("param1"));
    Assert.assertEquals("2",parentContext.getAttribute("param2"));
    Assert.assertEquals(null,parentContext.getAttribute("param3"));
    Assert.assertEquals("1",currentContext.getAttribute("param1"));
    Assert.assertEquals("4",currentContext.getAttribute("param2"));
    Assert.assertEquals("3",currentContext.getAttribute("param3"));
    Assert.assertEquals(null,currentContext.getAttribute("param4"));
    currentContext.removeAttribute("param1");
    currentContext.removeAttribute("param2");
    currentContext.removeAttribute("param3");
    currentContext.removeAttribute("param4");
    Assert.assertEquals("1",currentContext.getAttribute("param1"));
    Assert.assertEquals("2",currentContext.getAttribute("param2"));
    Assert.assertEquals(null,currentContext.getAttribute("param3"));
    Assert.assertEquals(null,currentContext.getAttribute("param4"));
  }
  