code: @Test public void testSetHeaders(){
    HeaderGroup headergroup=new HeaderGroup();
    Header header1=new BasicHeader("name1","value1");
    Header header2=new BasicHeader("name2","value2");
    Header header3=new BasicHeader("name3","value3");
    headergroup.addHeader(header1);
    headergroup.setHeaders(new Header[]{header2,header3});
    Assert.assertEquals(2,headergroup.getAllHeaders().length);
    Assert.assertEquals(0,headergroup.getHeaders("name1").length);
    Assert.assertFalse(headergroup.containsHeader("name1"));
    Assert.assertEquals(1,headergroup.getHeaders("name2").length);
    Assert.assertTrue(headergroup.containsHeader("name2"));
    Assert.assertEquals(1,headergroup.getHeaders("name3").length);
    Assert.assertTrue(headergroup.containsHeader("name3"));
    headergroup.setHeaders(null);
    Assert.assertEquals(0,headergroup.getAllHeaders().length);
  }
  