### Question:
AsyncFetcher implements Fetcher<K, V, E> { public static <K, V, E> Builder<K, V, E> builder() { return new Builder<>(); } @SuppressWarnings("WeakerAccess") protected  AsyncFetcher(Builder<K, V, E> builder); static Builder<K, V, E> builder(); @Override Registration poll(Consumer<K, V> consumer,
                             RecordConverter<K, V, E> recordConverter,
                             EventConsumer<E> eventConsumer); @Override void shutdown();  }### Answer:
@Test void testBuildingWithInvalidPollTimeoutShouldThrowAxonConfigurationException() { assertThrows(AxonConfigurationException.class, () -> AsyncFetcher.builder().pollTimeout(-5)); }
@Test void testBuildingWithInvalidExecutorServiceShouldThrowAxonConfigurationException() { assertThrows(AxonConfigurationException.class, () -> AsyncFetcher.builder().executorService(null)); }