Beyond Red/Green/Refactor: Testing as a mindset

“Red. Green. Refactor” is a great slogan for Test-Driven Development. It’s less great as a guide to actual TDD practice. The slogan provides no guidance for two very important questions in a TDD process: “What do I test next?” and “How do I break my problem into testable pieces”.

You may have struggled with TDD on these two issues, leading to giving up, or winding up with “uncanny valley” tests that are hard to maintain but don’t provide support for change. Using a puzzle problem, we’ll show how to expand on Red Green Refactor, so you can take advantage of the code-quality benefit of TDD.

Transcript

1. This slide is intentionally blank Noel Rappin, Beyond Red/Green/Refactor, WindyCityRails 2015. http://www.noelrappin.com | http://www.tablexi.com | @noelrap
2. Let's talk about drawing Noel Rappin, Beyond Red/Green/Refactor, WindyCityRails 2015. http://www.noelrappin.com | http://www.tablexi.com | @noelrap
3. How to draw Spider-Man Noel Rappin, Beyond Red/Green/Refactor, WindyCityRails 2015. http://www.noelrappin.com | http://www.tablexi.com | @noelrap
4. Step 1 Noel Rappin, Beyond Red/Green/Refactor, WindyCityRails 2015. http://www.noelrappin.com | http://www.tablexi.com | @noelrap
5. Step 2 Noel Rappin, Beyond Red/Green/Refactor, WindyCityRails 2015. http://www.noelrappin.com | http://www.tablexi.com | @noelrap
6. Done! Noel Rappin, Beyond Red/Green/Refactor, WindyCityRails 2015. http://www.noelrappin.com | http://www.tablexi.com | @noelrap
7. That's not enough information Noel Rappin, Beyond Red/Green/Refactor, WindyCityRails 2015. http://www.noelrappin.com | http://www.tablexi.com | @noelrap
8. In fact, those inital steps seem pointless Noel Rappin, Beyond Red/Green/Refactor, WindyCityRails 2015. http://www.noelrappin.com | http://www.tablexi.com | @noelrap
9. You end up with all these unnecssary lines Noel Rappin, Beyond Red/Green/Refactor, WindyCityRails 2015. http://www.noelrappin.com | http://www.tablexi.com | @noelrap
10. That just need to be erased Noel Rappin, Beyond Red/Green/Refactor, WindyCityRails 2015. http://www.noelrappin.com | http://www.tablexi.com | @noelrap
11. Maybe the person who taught you just wants to sell you erasers Noel Rappin, Beyond Red/Green/Refactor, WindyCityRails 2015. http://www.noelrappin.com | http://www.tablexi.com | @noelrap
12. Drawing with lines and ovals Doesn't work Noel Rappin, Beyond Red/Green/Refactor, WindyCityRails 2015. http://www.noelrappin.com | http://www.tablexi.com | @noelrap
13. The relationship between steps is complex Noel Rappin, Beyond Red/Green/Refactor, WindyCityRails 2015. http://www.noelrappin.com | http://www.tablexi.com | @noelrap
14. Beyond Red/Green/Refactor Testing as a Mindset Noel Rappin, Table XI Noel Rappin, Beyond Red/Green/Refactor, WindyCityRails 2015. http://www.noelrappin.com | http://www.tablexi.com | @noelrap
15. We've had a debate about TDD Noel Rappin, Beyond Red/Green/Refactor, WindyCityRails 2015. http://www.noelrappin.com | http://www.tablexi.com | @noelrap
16. I learned that I have been a bad TDD advocate Noel Rappin, Beyond Red/Green/Refactor, WindyCityRails 2015. http://www.noelrappin.com | http://www.tablexi.com | @noelrap
17. TDD is easy! isn't it? Noel Rappin, Beyond Red/Green/Refactor, WindyCityRails 2015. http://www.noelrappin.com | http://www.tablexi.com | @noelrap
18. Red Noel Rappin, Beyond Red/Green/Refactor, WindyCityRails 2015. http://www.noelrappin.com | http://www.tablexi.com | @noelrap
19. Green Noel Rappin, Beyond Red/Green/Refactor, WindyCityRails 2015. http://www.noelrappin.com | http://www.tablexi.com | @noelrap
20. Refactor Noel Rappin, Beyond Red/Green/Refactor, WindyCityRails 2015. http://www.noelrappin.com | http://www.tablexi.com | @noelrap
21. Red/Green/Refactor is a slogan not an instruction manual Noel Rappin, Beyond Red/Green/Refactor, WindyCityRails 2015. http://www.noelrappin.com | http://www.tablexi.com | @noelrap
22. I may not have made the motivations for TDD clear Noel Rappin, Beyond Red/Green/Refactor, WindyCityRails 2015. http://www.noelrappin.com | http://www.tablexi.com | @noelrap
23. I didn't want to scare people away from TDD Noel Rappin, Beyond Red/Green/Refactor, WindyCityRails 2015. http://www.noelrappin.com | http://www.tablexi.com | @noelrap
24. Like Object-Oriented design, small problems don't show TDD well Noel Rappin, Beyond Red/Green/Refactor, WindyCityRails 2015. http://www.noelrappin.com | http://www.tablexi.com | @noelrap
25. Fully implemented TDD solutions are boring to read about Noel Rappin, Beyond Red/Green/Refactor, WindyCityRails 2015. http://www.noelrappin.com | http://www.tablexi.com | @noelrap
26. I may have diminished the value of TDD Noel Rappin, Beyond Red/Green/Refactor, WindyCityRails 2015. http://www.noelrappin.com | http://www.tablexi.com | @noelrap
27. Noel Rappin, Beyond Red/Green/Refactor, WindyCityRails 2015. http://www.noelrappin.com | http://www.tablexi.com | @noelrap
28. There's still missing information Noel Rappin, Beyond Red/Green/Refactor, WindyCityRails 2015. http://www.noelrappin.com | http://www.tablexi.com | @noelrap
29. How do I know what ovals and lines to make? How do I know when each step is done? What if I want to draw Ms. Marvel instead? Noel Rappin, Beyond Red/Green/Refactor, WindyCityRails 2015. http://www.noelrappin.com | http://www.tablexi.com | @noelrap
30. Why are ovals and lines a good way to draw Spider-Man? Noel Rappin, Beyond Red/Green/Refactor, WindyCityRails 2015. http://www.noelrappin.com | http://www.tablexi.com | @noelrap
31. How do I decide what to test next? How do I know when I'm done? What do I refactor? Noel Rappin, Beyond Red/Green/Refactor, WindyCityRails 2015. http://www.noelrappin.com | http://www.tablexi.com | @noelrap
32. Why is test-first a good way to write software? Noel Rappin, Beyond Red/Green/Refactor, WindyCityRails 2015. http://www.noelrappin.com | http://www.tablexi.com | @noelrap
33. Encourages you to think about the problem In small, focused steps In a way that reinforces specific good practices Noel Rappin, Beyond Red/Green/Refactor, WindyCityRails 2015. http://www.noelrappin.com | http://www.tablexi.com | @noelrap
34. What is sometimes called "outside-in" testing is a special case Noel Rappin, Beyond Red/Green/Refactor, WindyCityRails 2015. http://www.noelrappin.com | http://www.tablexi.com | @noelrap
35. Write a test Make it pass with an incomplete implementation Write a more focused test Noel Rappin, Beyond Red/Green/Refactor, WindyCityRails 2015. http://www.noelrappin.com | http://www.tablexi.com | @noelrap
36. Broad tests that catch lots of errors Focused tests that drive design and show where the error is Noel Rappin, Beyond Red/Green/Refactor, WindyCityRails 2015. http://www.noelrappin.com | http://www.tablexi.com | @noelrap
37. A lot of problems seem easy to acceptance test But hard to unit test Noel Rappin, Beyond Red/Green/Refactor, WindyCityRails 2015. http://www.noelrappin.com | http://www.tablexi.com | @noelrap
38. "What to test next" is a design question Noel Rappin, Beyond Red/Green/Refactor, WindyCityRails 2015. http://www.noelrappin.com | http://www.tablexi.com | @noelrap
39. Given a sequence of digits 1 to 9, such as [1, 1, 2, 3, 8] 4 The sum is 15 4 At least one digit appears exactly twice 4 No digit appears more than twice 4 Order is irrelevant Noel Rappin, Beyond Red/Green/Refactor, WindyCityRails 2015. http://www.noelrappin.com | http://www.tablexi.com | @noelrap
40. code at https://github.com/noelrappin/spec_sequence Noel Rappin, Beyond Red/Green/Refactor, WindyCityRails 2015. http://www.noelrappin.com | http://www.tablexi.com | @noelrap
41. Here's what might be the most obivous test: it "knows a valid sequence" do expect(Sequence.new(1, 1, 2, 3, 8)).to be_valid end Noel Rappin, Beyond Red/Green/Refactor, WindyCityRails 2015. http://www.noelrappin.com | http://www.tablexi.com | @noelrap
42. And then we would make that test pass... Noel Rappin, Beyond Red/Green/Refactor, WindyCityRails 2015. http://www.noelrappin.com | http://www.tablexi.com | @noelrap
43. Wait, How would we make that test pass? Noel Rappin, Beyond Red/Green/Refactor, WindyCityRails 2015. http://www.noelrappin.com | http://www.tablexi.com | @noelrap
44. We could write the whole algorithm Noel Rappin, Beyond Red/Green/Refactor, WindyCityRails 2015. http://www.noelrappin.com | http://www.tablexi.com | @noelrap
45. But that is not letting the test drive the design Noel Rappin, Beyond Red/Green/Refactor, WindyCityRails 2015. http://www.noelrappin.com | http://www.tablexi.com | @noelrap
46. Instead, let's take a small step Noel Rappin, Beyond Red/Green/Refactor, WindyCityRails 2015. http://www.noelrappin.com | http://www.tablexi.com | @noelrap
47. class Sequence def init(*items) @items = items end def valid? true end end Noel Rappin, Beyond Red/Green/Refactor, WindyCityRails 2015. http://www.noelrappin.com | http://www.tablexi.com | @noelrap
48. This makes the test pass Noel Rappin, Beyond Red/Green/Refactor, WindyCityRails 2015. http://www.noelrappin.com | http://www.tablexi.com | @noelrap
49. This is OK Noel Rappin, Beyond Red/Green/Refactor, WindyCityRails 2015. http://www.noelrappin.com | http://www.tablexi.com | @noelrap
50. Because it is not permanent Noel Rappin, Beyond Red/Green/Refactor, WindyCityRails 2015. http://www.noelrappin.com | http://www.tablexi.com | @noelrap
51. It's sometimes called "sliming the test" Noel Rappin, Beyond Red/Green/Refactor, WindyCityRails 2015. http://www.noelrappin.com | http://www.tablexi.com | @noelrap
52. Okay, now what? Noel Rappin, Beyond Red/Green/Refactor, WindyCityRails 2015. http://www.noelrappin.com | http://www.tablexi.com | @noelrap
53. First option: Stay at same abstraction level Write a test case that fails Noel Rappin, Beyond Red/Green/Refactor, WindyCityRails 2015. http://www.noelrappin.com | http://www.tablexi.com | @noelrap
54. Broken code it "knows a valid sequence" do expect(Sequence.new(1, 1, 2, 3, 9)).not_to be_valid end Noel Rappin, Beyond Red/Green/Refactor, WindyCityRails 2015. http://www.noelrappin.com | http://www.tablexi.com | @noelrap
55. Normally a good option Noel Rappin, Beyond Red/Green/Refactor, WindyCityRails 2015. http://www.noelrappin.com | http://www.tablexi.com | @noelrap
56. In this case, though, it leads to another round of "how do we make this pass?" Noel Rappin, Beyond Red/Green/Refactor, WindyCityRails 2015. http://www.noelrappin.com | http://www.tablexi.com | @noelrap
57. Rule of thumb: If it's not clear how you might make a test pass, there's probably a smaller test Noel Rappin, Beyond Red/Green/Refactor, WindyCityRails 2015. http://www.noelrappin.com | http://www.tablexi.com | @noelrap
58. Option 2 Go to a less abstract or smaller piece Write a failing test there Noel Rappin, Beyond Red/Green/Refactor, WindyCityRails 2015. http://www.noelrappin.com | http://www.tablexi.com | @noelrap
59. Searching for that smaller test is where design happens Noel Rappin, Beyond Red/Green/Refactor, WindyCityRails 2015. http://www.noelrappin.com | http://www.tablexi.com | @noelrap
60. (Sometimes, that smaller test is not worth writing) Noel Rappin, Beyond Red/Green/Refactor, WindyCityRails 2015. http://www.noelrappin.com | http://www.tablexi.com | @noelrap
61. A more focused test might be: Part of the job One of the cases An error case Noel Rappin, Beyond Red/Green/Refactor, WindyCityRails 2015. http://www.noelrappin.com | http://www.tablexi.com | @noelrap
62. In this case: easy to target the individual clauses (sum of 15, has a pair, etc..) Noel Rappin, Beyond Red/Green/Refactor, WindyCityRails 2015. http://www.noelrappin.com | http://www.tablexi.com | @noelrap
63. A smaller test it "can tell if the sum is 15" do expect(Sequence.new(7, 8).to be_correct_sum) end Noel Rappin, Beyond Red/Green/Refactor, WindyCityRails 2015. http://www.noelrappin.com | http://www.tablexi.com | @noelrap
64. Why is that better? Noel Rappin, Beyond Red/Green/Refactor, WindyCityRails 2015. http://www.noelrappin.com | http://www.tablexi.com | @noelrap
65. Because it's small enough that I can write it without thinking too hard Noel Rappin, Beyond Red/Green/Refactor, WindyCityRails 2015. http://www.noelrappin.com | http://www.tablexi.com | @noelrap
66. Like so def correct_sum? items.inject(:+) == 15 end Noel Rappin, Beyond Red/Green/Refactor, WindyCityRails 2015. http://www.noelrappin.com | http://www.tablexi.com | @noelrap
67. I don't need to slime this test Noel Rappin, Beyond Red/Green/Refactor, WindyCityRails 2015. http://www.noelrappin.com | http://www.tablexi.com | @noelrap
68. Also, I can negate it easily it "can tell if the sum is not 15" do expect(Sequence.new(7, 8, 1).not_to be_correct_sum) end Noel Rappin, Beyond Red/Green/Refactor, WindyCityRails 2015. http://www.noelrappin.com | http://www.tablexi.com | @noelrap
69. TDD should reduce cognitive load Noel Rappin, Beyond Red/Green/Refactor, WindyCityRails 2015. http://www.noelrappin.com | http://www.tablexi.com | @noelrap
70. So from here, I can do 4 has a digit pair 4 does not have a digit trio 4 is unique Noel Rappin, Beyond Red/Green/Refactor, WindyCityRails 2015. http://www.noelrappin.com | http://www.tablexi.com | @noelrap
71. Once those are in place, the not_valid test is simpler Noel Rappin, Beyond Red/Green/Refactor, WindyCityRails 2015. http://www.noelrappin.com | http://www.tablexi.com | @noelrap
72. A plan: Noel Rappin, Beyond Red/Green/Refactor, WindyCityRails 2015. http://www.noelrappin.com | http://www.tablexi.com | @noelrap
73. Start with a broad test Noel Rappin, Beyond Red/Green/Refactor, WindyCityRails 2015. http://www.noelrappin.com | http://www.tablexi.com | @noelrap
74. Find a piece that can be encapsulated Noel Rappin, Beyond Red/Green/Refactor, WindyCityRails 2015. http://www.noelrappin.com | http://www.tablexi.com | @noelrap
75. Test a happy-path solution Noel Rappin, Beyond Red/Green/Refactor, WindyCityRails 2015. http://www.noelrappin.com | http://www.tablexi.com | @noelrap
76. Try to break it Noel Rappin, Beyond Red/Green/Refactor, WindyCityRails 2015. http://www.noelrappin.com | http://www.tablexi.com | @noelrap
77. Where did design come in? Noel Rappin, Beyond Red/Green/Refactor, WindyCityRails 2015. http://www.noelrappin.com | http://www.tablexi.com | @noelrap
78. I design my functionality as I write the end-to-end test Noel Rappin, Beyond Red/Green/Refactor, WindyCityRails 2015. http://www.noelrappin.com | http://www.tablexi.com | @noelrap
79. I design my code structure as I break the code up Noel Rappin, Beyond Red/Green/Refactor, WindyCityRails 2015. http://www.noelrappin.com | http://www.tablexi.com | @noelrap
80. I design my internal API as I write the happy-path test Noel Rappin, Beyond Red/Green/Refactor, WindyCityRails 2015. http://www.noelrappin.com | http://www.tablexi.com | @noelrap
81. I refactor to keep my design clean Noel Rappin, Beyond Red/Green/Refactor, WindyCityRails 2015. http://www.noelrappin.com | http://www.tablexi.com | @noelrap
82. Sarah Mei Noel Rappin, Beyond Red/Green/Refactor, WindyCityRails 2015. http://www.noelrappin.com | http://www.tablexi.com | @noelrap
83. code at https://github.com/noelrappin/spec_sequence Noel Rappin, Beyond Red/Green/Refactor, WindyCityRails 2015. http://www.noelrappin.com | http://www.tablexi.com | @noelrap
84. Noel Rappin Table XI (tablexi.com) @noelrap 4 http://www.noelrappin.com/trdd 4 http://pragprog.com/book/nrtest2/rails-4-test- prescriptions 4 http://www.patreon.com/noelrap Noel Rappin, Beyond Red/Green/Refactor, WindyCityRails 2015. http://www.noelrappin.com | http://www.tablexi.com | @noelrap