code: @Test public void merge(){
    Settings a=new Settings();
    a.set(UPLOAD_BANDWIDTH,PERSIST_VALUE,100);
    a.set(DOWNLOAD_BANDWIDTH,PERSIST_VALUE,200);
    a.set(DOWNLOAD_RETRANS_RATE,0,300);
    Settings b=new Settings();
    b.set(DOWNLOAD_BANDWIDTH,0,400);
    b.set(DOWNLOAD_RETRANS_RATE,PERSIST_VALUE,500);
    b.set(MAX_CONCURRENT_STREAMS,PERSIST_VALUE,600);
    a.merge(b);
    assertEquals(100,a.getUploadBandwidth(-1));
    assertEquals(PERSIST_VALUE,a.flags(UPLOAD_BANDWIDTH));
    assertEquals(400,a.getDownloadBandwidth(-1));
    assertEquals(0,a.flags(DOWNLOAD_BANDWIDTH));
    assertEquals(500,a.getDownloadRetransRate(-1));
    assertEquals(PERSIST_VALUE,a.flags(DOWNLOAD_RETRANS_RATE));
    assertEquals(600,a.getMaxConcurrentStreams(-1));
    assertEquals(PERSIST_VALUE,a.flags(MAX_CONCURRENT_STREAMS));
  }
  