private void completeShareUnsubscribeApplicationEventSuccessfully() {
        doAnswer(invocation -> {
            ShareUnsubscribeEvent event = invocation.getArgument(0);
            event.future().complete(null);
            return null;
        }).when(applicationEventHandler).add(ArgumentMatchers.isA(ShareUnsubscribeEvent.class));
    }
Tests {@link ShareConsumerImpl#processBackgroundEvents(Future, Timer) processBackgroundEvents}
handles the case where the {@link Future} does not complete within the timeout.
clients/src/test/java/org/apache/kafka/clients/consumer/internals/ShareConsumerImplTest.java