This talk is about experiments with RSpec files changing the files through the abstract syntax tree. It works with the Ruby gem fast: https://github.com/jonatas/fast that allow running dynamic experiments manipulating code and running the changed code

1. ex-specs
@jonatasdp

2. HowI discovered
3k lines of USELESS
code in a week

3. NO broken builds
¯_(ツ)_/¯

5. Experiments
Autonomous

6. Context
- Huge codebase
- Mechanical task
- Meaningless work

7. Legacy specs

8. It was a good idea when it was written

9. Things get old

10. “You don’t stop doing things
because you get old.
You get oldbecause you stop
doing things.”
Rosamunde Pilcher

11. “The codedoes not get old
because we don’t run it.
It get oldbecause we stop
changing it.”
Jônatas

12. Old things are not BAD

13. We just start new things
EVERYDAY

14. HUGEcodebases

15. Dozens of
teams

16. Pull Requests
changing code
everywhere

17. MY FOCUS

18. Legacy specs

19. INTERESTING
RESULTS

20. ALL ||NOTHING
BAD STRATEGY

21. I need
independent
replacers

22. WRITE
it down.

23. http://ideia.me

24. Divide &
conquer

25. Experiments allow us to…
➔ Test “what if…”
➔ Find useless code and commit same mistakes
➔ Avoid repeating same experiments
➔ Like a linter but it’s not a linter

26. Simple 1 to 1 combination used to
generate the next interaction
Combining
experiments

27. Same experiment

28. Replace `create`
with
`build_stubbed`

29. 1
Third experiment
Remove useless blocks options

30. Fast.experiment

31. 1
https://github.com/jonatas/fast#experiments
Last experiment
Remove before/after blocks

32. Component Browser
Experiment identifier

33. Component Browser
What files it should lookup:

34. Component Browser
Use the node pattern to find the target nodes

35. Use parser gem
Code
Representation

42. Component Browser
Balsamiq Tip | Use the Balsamiq add-on to make your own wireframe.
What should be done in the target node

43. Parser::Writer ● remove(range)
● insert_after(position, content)
● insert_before(position, content)
Very simple interface to rewrite
code file based on AST

44. Component Browser
Policy: Is it a good change?

45. Find stubbed methods being called without
parameters and check the parameters signature.
Using fast as a research tool

46. Example

47. Mock cases

48. Method Signature

49. Example of the research

50. Using bundler/inline is cool

51. Hunting for method signatures compatibility

52. Experiments
will not save youfrom thinking.
Only automate some repetitive tasks.

53. Let’s code!!!

54. Next Steps > Fast#experiments
● Public experiments suite
● Run multiple checkers
● Check only diff nodes
● Improve combination strategy
● Implement “fast --warn” to report issues

55. “You don’t stop doing things
because you get old.
You get oldbecause you stop
doing things.”
Rosamunde Pilcher

56. References
https://github.com/jonatas/fast#fastexperiment
http://ideia.me/the-dynamic-experiment-initiative
http://ideia.me/adventures-on-automated-code-replacement
https://gist.github.com/jonatas/c1e580dcb74e20d4f2df4632ceb084ef

57. Questions
? @jonatasdphttp://ideia.me

58. @jonatasdp
T h a n k s !