Ok, so the problem I'd like to solve is having tests in CI being overly verbose. Now I could turn down the logging in general, but that would hurt when you actually need to debug one. What I think I'd like to do is accumulate all the logs in memory, and then set the actual level to emit when the suite has errored or succeeded, then emit/append the logs that need to be. Bonus points if I could somehow do this by inspecting the exception stack when it fails. Is this possible?
possible duplicate really it's the same question, but in 6 years we've gotten log4j2 and junit5, so I guess I'm wondering if this has changed.
Nope, that watcher is still it (write your own, in other words), because your request is still bizarre. Time isn't going to change this.
Logging frameworks love to write ASAP, not later. After all, maybe the VM is about to hard-crash and that is the absolute worst time of all to cache some writes - the very log statements that provide insights into the hard crash are now lost to the ether.
Normally, the solution is to use tools that read the log files and process them in some fashion - usually, by chucking most of the lines out as you copy and zip them up for the ages, keeping the full dump (and uncompressed) only for the most recent few logs.
Key principle there being: A separate process (may not even be written in java) that does this later.
Can you configure your CI system to do this? That sounds like the right approach: Log at a pretty verbose level, and have the CI system strip the logs down to a much more strict level after the tests ran if the tests were successful.