@Test
  public void cannotReadOnceClosed() throws IOException, InterruptedException, ExecutionException {
    final File path = tmp.newFile();
    final Env<ByteBuffer> env = create()
            .setMaxReaders(5)
            .open(path, MDB_NOSUBDIR);

    final Dbi<ByteBuffer> dbi = env.openDbi(DB_1, MDB_CREATE);

    dbi.put(bb(1), bb(10));
    dbi.put(bb(2), bb(20));

    try (Txn<ByteBuffer> roTxn = env.txnRead()) {
      assertThat(dbi.get(roTxn, bb(1)).getInt(), is(10));
      assertThat(dbi.get(roTxn, bb(2)).getInt(), is(20));
    }

    System.out.println("Done puts");

    final CountDownLatch firstGetFinishedLatch = new CountDownLatch(1);
    final CountDownLatch envClosedLatch = new CountDownLatch(1);

    final CompletableFuture<Void> future = CompletableFuture.runAsync(() -> {

      System.out.println("Running async task");
      try (Txn<ByteBuffer> roTxn = env.txnRead()) {
        try (CursorIterable<ByteBuffer> iterable = dbi.iterate(roTxn, KeyRange.all())) {
          final Iterator<CursorIterable.KeyVal<ByteBuffer>> iterator = iterable.iterator();

          try {
            System.out.println("Getting first entry");
            CursorIterable.KeyVal<ByteBuffer> keyVal = iterator.next();
            assertThat(keyVal.val().getInt(), is(10));

            firstGetFinishedLatch.countDown();

            try {
              System.out.println("Waiting for env to close");
              envClosedLatch.await();
            } catch (InterruptedException e) {
              Thread.currentThread().interrupt();
              throw new RuntimeException(e);
            }

            assertThat(env.isClosed(), is(true));

            System.out.println("Getting second entry, but env is now closed");
            keyVal = iterator.next();
            assertThat(keyVal.val().getInt(), is(20));
          } catch (RuntimeException e) {
            e.printStackTrace();
          }
        }
      }
    });

    System.out.println("Waiting for cursor to get first entry");
    firstGetFinishedLatch.await();

    System.out.println("Closing env");
    env.close();
    envClosedLatch.countDown();

    System.out.println("Waiting for completion");
    future.get();
  }