private void expectMemberPoll() {
        ArgumentCaptor<Supplier<UncheckedCloseable>> onPoll = ArgumentCaptor.forClass(Supplier.class);
        doAnswer(invocation -> {
            onPoll.getValue().get().close();
            return null;
        }).when(member).poll(anyLong(), onPoll.capture());
    }
Issues multiple rapid fencing requests for a handful of connectors, each of which takes a little while to complete.
This mimics what might happen when a few connectors are reconfigured in quick succession and each task for the
connector needs to hit the leader with a fencing request during its preflight check.
connect/runtime/src/test/java/org/apache/kafka/connect/runtime/distributed/DistributedHerderTest.java