> “ The cost of a bug slipping through because a test being skipped will be higher than running an irrelevant test to a commit.”
It really depends on the type of bug, and perhaps this could be factored into the model by also correlating change sets with outage severity or complexity of a fix.
"A bug slipping through" in this case just means slipping through to where it's detected on a later push to the integration branch, or failing that, when a more complete set of tests runs when the change is merged into the main branch. In no case will poor scheduling here result in a bug making it into the final product. It's just that it's more costly in human time to detect it later, so currently the entire goal is set at detecting the problem on the first round of testing after a push.
It really depends on the type of bug, and perhaps this could be factored into the model by also correlating change sets with outage severity or complexity of a fix.