Debugging

Presentation about debugging for people just learning to program.

1. Wojciech @sharnik haikuco.de
2. Programming is like riding a bike.
3. Except the bike is on fire and you're on fire and everything is on fire and you're actually in hell.
5. Main programming tasks: » Adding bugs » Removing bugs
6. Debugging
7. Know what you're trying to do
8. Inputs -> Program -> Outputs Calculator.add(2, 3) # => 5
9. Workflow
10. Reproduce the error
11. Make a hypothesis
12. Fix
13. Profit
14. If that didn't help, rollback
15. Techniques
16. Puts debugging class Calculator def add(a, b) puts a puts b a + b end end result = Calculator.new.add(2, 3) puts result
17. strings vs numbers ruby -e "x = 3; puts x" # => 3 ruby -e "x = '3'; puts x" # => 3 ruby -e "x = 3; puts x.inspect" # => 3 ruby -e "x = '3'; puts x.inspect" # => "3"
18. p: shorter puts X.inspect class Calculator def add(a, b) p a p b a + b end end result = Calculator.new.add(2, 3) p result
19. debugger: pry + byebug require 'pry-byebug' class Calculator def add(a, b) binding.pry a + b end end Calculator.new.add(2, 3)
20. Strategies
21. "Wolf fence" algorithm
22. Rubber duck debugging
23. Practice
24. Exercise gist.github.com/sharnik/2aedd681e6bcf81a7697 Remember » understand expectations » pinpoint where the bug is » find what the bug is » fix it