Hello - I didn't see an answer posted to this, so here are some thoughts:
There is no line-by-line coverage check, only function/rule-level coverage - in the logs, you should find both a Rule name and a Virtual Server name that tags along with each log.info() entry, something like:
[23/Aug/2019:18:23:18 +0200] INFO rules/example rulelogmsginfo vservers/example Hello World!
If needed, you can add extra messages using statements of the form:
log.info( ... ); or
log.debug( ... );
However, make sure you don't create too many extra log entries, as this can flood the logfile and make it difficult to read.