If your application produces a new folder whenever it generates files AND writes an application log, it is NOT enough to check if the newly created folder exists to infer that all went well.
Example given, last time that we were following an issue (apparently) concerning missing data we discovered that the operator - who fired the missing data issue - had started the elaboration but did not check the logs. If he did he would have easily discover that the log was truncated not only in the middle of the elaboration, but also in the middle of a row. If he also checked the system log he would have just as easily spotted a system crash with subsequent reboot. And he would start the elaboration again. <irony>And he would not have dared to disturb us</irony>, but most of all he would not have alarmed the customer, leaving him with some doubts on the integrity of the system.
Unluckily, logs are just another thing like manuals: nobody reads them. I wonder whether there's an equivalent for RTFM... RTFL? No, that's not ROTFL, just the opposite...
Thanks to Antonio for letting me shoot his logs.