code: @Test public void clearOnChildThreadShouldNotAffectParent() throws InterruptedException {
    String firstKey="x" + diff;
    String secondKey="o" + diff;
    mdcAdapter.put(firstKey,firstKey + A_SUFFIX);
    assertEquals(firstKey + A_SUFFIX,mdcAdapter.get(firstKey));
    Thread clearer=new ChildThread(mdcAdapter,firstKey,secondKey){
      @Override public void run(){
        mdcAdapter.clear();
        assertNull(mdcAdapter.get(firstKey));
      }
    }
  ;
    clearer.start();
    clearer.join();
    assertEquals(firstKey + A_SUFFIX,mdcAdapter.get(firstKey));
  }
  