void assertReceivedItemCount(final int count) {
        TestUtil.waitForIt(
                () -> {
                    final long actualCount = getDataFeedRequests()
                            .stream()
                            .map(DataFeedRequest::getDataFeedRequestItems)
                            .flatMap(Collection::stream)
                            .filter(item -> item.type.equals(StroomZipFileType.META.getExtension()))
                            .count();
                    return actualCount;
                },
                (long) count,
                () -> "Received item count",
                Duration.ofMinutes(1),
                Duration.ofMillis(100),
                Duration.ofSeconds(1));

        final long actualCount = getDataFeedRequests()
                .stream()
                .map(DataFeedRequest::getDataFeedRequestItems)
                .flatMap(Collection::stream)
                .filter(item -> item.type.equals(StroomZipFileType.META.getExtension()))
                .count();
        Assertions.assertThat(actualCount)
                .isEqualTo(count);
    }
Assert that a http header is present and has this value
stroom-proxy/stroom-proxy-app/src/test/java/stroom/proxy/app/MockHttpDestination.java