code: private byte[] generateAesKey() {
          byte[] bytes = new byte[32];
          if (!testMode) {
              SecureRandom random = new SecureRandom();
              random.nextBytes(bytes);
          } else {
              bytes = "TEST1234TEST1234TEST1234TEST1234".getBytes(MESSAGE_ENCODING);
          }
          return bytes;
      }
docs: Generates AES key.
  
  @return Random AES key or pre-defined value for test mode.