Luca's add-pktgen-and-testpmd-changes series is highlighting to me that we are
now providing a few paths for traffic validation through DTS, and testsuite
validation through testpmd queries. In the spirit of the goal of making DTS a
framework where people can start using it from no knowledge, and write a simple
testsuite in a matter of minutes, not hours, it probably makes sense to
organize some common strategies for testsuite validation through traffic
validation and/or testpmd queries, so new users can copy those strategies
easily. Jotting down a few high level notes for this below, but I can write
something more comprehensive for this doc patch. 

1. Send and store the returned packet list using send_packets_and_capture(),
build expected returned packet list by mapping the packet list with
get_expected_packet(), then compare the two using
sendtestsuite.match_all_packets()
    optional: User can also leverage framework/utils.py
generate_random_packets() to build a list of packets which can be used with the
above process, if desired. 

2. Build a packet with a known payload, like:
        packet = Ether() / IP() / Raw("XXXXXXXXX")
    And then send the packet with testsuite.send_packet_and_capture, iterate
through the returned list, checking for a packet with that Raw layer contents.

3. Can also validate using the info returned by testpmd with show port info,
verbose output, etc.