@After
  public void postCheck() {
    if (router != null) {
      if (router.isOpen()) {
        router.close();
      }
    }
    nettyByteBufLeakHelper.afterTest();
  }
Every test in this class should leave the router closed in the end. Some tests do additional checks after
closing the router. This is just a guard to ensure that the tests are not broken (which helped when developing
these tests).
ambry-router/src/test/java/com/github/ambry/router/PutManagerTest.java