How to debug functions at Doc Level?

Personally, I don't use the debugger. I find it clunky and awkward to use. I prefer to add commands to print out the values of the variables I'm interested in to the console at various points in the code.

The debugger doesn't "catch bugs". It reports errors. Many bugs just do the wrong thing, without gerring an error. 

You will get error messages when you use the functions and there are errors in the functions.