This sounds like a good idea, in order to catch issues like this in the future during trybot runs.
@bradfitz The js-wasm builder currently has numTryTestHelpers set to 4, which seems quite close to most other builders. What do you think would be a good number to set it to in order to be able js-wasm trybot to run all dist tests? Any suggestions on how to evaluate how that number correlates to the trybot execution time?
I wouldn't even try to correlate it with numTryTestHelpers historical values.
You should be able to pick a goal time (5 or 6 minutes), subtract empirical make.bash time, and then that's the amount of time to you have to run all the tests. So find the sum of all the test durations for js-wasm and divide, and that's the shard count you want.