Stop using development mode

Rails development mode is easy, useful and fast: we can spin up an app, edit its source, hit reload in a browser and see the result of our changes. But what effect does this workflow have on our code, and does it really help us? In this talk I look at the dark side of development mode — where it falls down, what it does wrong, and how it ultimately encourages us to develop software in the wrong way — and suggest an alternative way of working which avoids these disadvantages.

Given at Railsberry (http://railsberry.com/). There's a video of this talk at http://youtu.be/TQrEKwb5lR0.

Transcript

1. Stop using development mode. by @tomstuart, at Railsberry, in Kraków, on 2012-04-20.
2. How to develop a Rails application:
3. RAILS_ENV=development
4. config/environments/ development.rb: config.cache_classes = false
5. $ rails server
18. (That was 2005.)
19. Development mode is what first got me excited about Rails.
20. Reload-driven development ™
21. What’s wrong with this methodology?
22. cowboy programming testless programming inside-out programming it encourages:
23. Cowboy programming
24. programming before thinking pressing reload until it looks like it’s working writing the code you want to write
25. Testless programming
26. why write tests when you can press reload?
27. PRESSING RELOAD DOESN’T SCALE
28. why write tests when you can press reload? the app works! now write tests so you don’t feel guilty the app broke! now write tests so it doesn’t break again
29. THE DEFINITION OF WORKING IS THAT THE TESTS PASS
30. Inside-out programming
31. write a migration write a model write a controller write a template write a route press reload
32. database.
33. database. model.
34. database. model. controller.
35. database. model. controller. template.
36. database. model. controller. template. route. user.
37. You build each layer before you’ve built the layer that uses it.
38. You are imagining what the next layer will need this one to do.
39. If you love imagining things that much,
40. move to Los Angeles
41. and become a Scientologist.
42. Development mode doesn’t let you see anything working until you’ve completed a full vertical slice through the application.
43. This makes it easier to write badly designed code.
44. If Rails has a development mode, shouldn’t I use it?
46. What’s a “web framework”?
47. “A collection of libraries, utilities and conventions to make web application development easier.”
48. You are right and good.
49. “A note from my mother excusing me from responsibility for every decision.”
50. YOUR FAULT YOU ARE WRONG AND BAD EVERYTHING IS
51. Rails is software. It doesn’t care about you.
52. Be mindful. Use judgement.
53. There is a better way.
54. Two related ideas:
55. 1. Work outside-in.
56. Start by writing an acceptance test to explain the ultimate goal.
57. (An automated one.)
58. Drill down into the application by writing unit tests to set intermediate goals.
59. Make progress towards the ultimate goal by getting unit tests to pass, not by pressing reload.
60. Reach the ultimate goal by getting the acceptance test to pass, not by pressing reload.
61. (During development, your primary clients are automated tests, not web browsers.)
62. How is this possible? How can you test the controller before writing the model?
63. 2. Use mocking.
64. Ruby is inspired by Smalltalk.
65. Smalltalk says: a program is a network of collaborating objects.
67. Reboot your brain to think in terms of object collaboration.
68. Drive out the design of objects using mocking, not guessing.
69. mock these unit test this
70. You can implement an object before its collaborators exist.
71. By the time you start implementing them, you’ll already know what they need to do.
72. It’s not about coverage, it’s about driving your design directly at every level.
73. The only limitation is your acceptance tests.
74. Some automated tests are too hard, or impossible, to write.
75. Fine: use development mode to run those acceptance tests with your eyes and brain.
76. Why work this way?
77. Better design. Better code. Less pressing reload. Faster tests.
78. It is possible to build a web application without opening a web browser.
79. “Do I need to use development mode?”
80. In practice:
81. growing-object-oriented-software.com
82. pragprog.com/book/achbd/the-rspec-book
83. Thank you. @tomstuart / tom@experthuman.com / computationbook.com