code: @Test public void findSessionId(){
    HttpServerExchange exchange=new HttpServerExchange(null);
    when(this.config.findSessionId(exchange)).thenReturn(null);
    String result=this.subject.findSessionId(exchange);
    assertNull(result);
    String encodedSessionId="session.route1";
    String sessionId="session";
    when(this.config.findSessionId(exchange)).thenReturn(encodedSessionId);
    when(this.codec.decode(encodedSessionId)).thenReturn(sessionId);
    when(this.codec.encode(sessionId)).thenReturn(encodedSessionId);
    result=this.subject.findSessionId(exchange);
    assertSame(sessionId,result);
    verify(this.config,never()).setSessionId(same(exchange),anyString());
    String reencodedSessionId="session.route2";
    when(this.codec.encode(sessionId)).thenReturn(reencodedSessionId);
    result=this.subject.findSessionId(exchange);
    assertSame(sessionId,result);
    verify(this.config).setSessionId(exchange,reencodedSessionId);
  }
  