Validate correctness of Usage events

One of the topics my team is very interested is in verifying the correctness of the events that are generated by performing API requests to the various APIs (the compute ones are specified at http://wiki.openstack.org/SystemUsageData). We've seen issues before where fields in these messages are incorrect or not even present, so we've devoted some time already towards this topic. These tests use integration points that not every deployment might have, so we would like to propose a more generic solution to testing this problem. Stacktach is actually great for this, but there are other options as well, or possibly Ceilometer as well for folks using it. These tests would be optional to use as it might not be within the realm of interest to everyone.