How do you debug plugins?
I have an issue that the posts table shows "no posts found" right after the installation although I can see "All (1) | Published (1)" right above it.
Now I'm not asking how to fix this very issue, I'd rather learn how to troubleshoot such issues in general. Is there a log file? (Haven't found one.) Is there some plugin that would help with seeing which SQL commands are executed and what data is returned? Something to display PHP warnings?