void assertMaxItemsPerAggregate(final Config config) {
        final List<DataFeedRequest> forwardFiles = getDataFeedRequests();
        final List<Long> aggItemCounts = forwardFiles.stream()
                .map(DataFeedRequest::getDataFeedRequestItems)
                .map(zipItems -> zipItems.stream()
                        .filter(zipItem ->
                                zipItem.type().equals(StroomZipFileType.META.getExtension()))
                        .count())
                .toList();

        final AggregatorConfig aggregatorConfig = config.getProxyConfig().getAggregatorConfig();
        final int maxItemsPerAggregate = aggregatorConfig.getMaxItemsPerAggregate();

        // Each agg should be no bigger than configured max
        for (final Long itemCount : aggItemCounts) {
            Assertions.assertThat(itemCount)
                    .isLessThanOrEqualTo(maxItemsPerAggregate);
        }

        final StroomDuration aggregationFrequency = aggregatorConfig.getAggregationFrequency();
        final List<Duration> aggAges = forwardFiles.stream()
                .map(DataFeedRequest::getDataFeedRequestItems)
                .map(zipItems -> {
                    final LongSummaryStatistics stats = zipItems.stream()
                            .filter(zipItem ->
                                    zipItem.type().equals(StroomZipFileType.META.getExtension()))
                            .map(zipItem -> zipItem.getContentAsAttributeMap()
                                    .get(StandardHeaderArguments.RECEIVED_TIME))
                            .mapToLong(DateUtil::parseNormalDateTimeString)
                            .summaryStatistics();
                    return Duration.between(
                            Instant.ofEpochMilli(stats.getMin()),
                            Instant.ofEpochMilli(stats.getMax()));
                })
                .toList();

        // Each agg should have a receipt time range no wider than the configured max agg age
        for (final Duration aggAge : aggAges) {
            Assertions.assertThat(aggAge)
                    .isLessThanOrEqualTo(aggregationFrequency.getDuration());
        }
    }
Assert all the {@link UniqueId}s contained in the stored aggregates
stroom-proxy/stroom-proxy-app/src/test/java/stroom/proxy/app/MockHttpDestination.java