I'm not so sure what could be a condition for the performance test to pass, what i'm currently doing is subscribing to the pose/info topic of the pendulum and counts how many msgs is processed/received during a period of time of 4sec.
That sounds like a good approach. Here is my wish list of features:
The ability to change the time period "easily", (maybe by having a global variable at the top of the test file)
I would like to see the number of messages processed per second printed by the test (ex: 290 messages received in 4 seconds (72.5 messages/sec)
As for the condition for the test to pass or fail: I recommend that the test should pass as long as it receives a handful of messages. This is because the tests will be executed automatically on low performance machines whenever the gazebojs source code changes.