this was an issue I kinda just accepted when I wrote the test, but I just noticed that in db.serverStatus() there are counters for each aggregation stage. so here https://github.com/mongodb/mongo/blob/5d964e3645d349515a5c2edba2031d39b5aaa21f/jstests/sharding/query/pipeline_length_limit.js#L110 when we test a bunch of stages we can create a list of the stage names we've tested and assert we've done all the ones in server status and ignore the ones that don't make sense. this means if an agg stage is added then this test will fail and force the author to add it to the test. we could do something similar with the fuzzers potentially.