Property Based Testing on Rails

The Ruby community is known by its strong culture of testing, but this is not an excuse to refuse alternative approaches. One of these are Property Testing. In those tools we do not express examples, but the possible input formats; instead of specific outputs, characteristics that must remain true. In this way our tools are capable of exhaustively generate test cases and look for failures. In this talk we'll see how to create lean suites with wide coverage using Clojure's power to test a Rails application.

Video [pt-br]: https://www.youtube.com/watch?v=WKuZWzi2oRQ

Transcript

1. TESTES DE PROPRIEDADE (((on Rails)))
2. Eu ♥ Ruby!
3. Eu ♥ Clojure!
4. (((((((((((((yep!)))))))))))))
5. 4:20 PM
6. Andrew Rosa @_andrewhr
8. Prop… what?
9. it "sorts a list" do v = [3, 1, 2] s = sort(v) expect(s).to eq([1, 2, 3]) end
10. it "sorts a list" do v = [3, 1, 2] s = sort(v) expect(s).to eq([1, 2, 3]) end
11. it "sorts a list" do v = [3, 1, 2] s = sort(v) expect(s).to eq([1, 2, 3]) end
12. it "sorts a list" do v = [3, 1, 2] s = sort(v) expect(s).to eq([1, 2, 3]) end
13. it "sorts a list" do v = [3, 1, 2] s = sort(v) expect(s).to eq([1, 2, 3]) end
14. EXEMPLO
15. #sorts ascending sorts an empty list sorts a list with single item sorts a list with multiple items ! Finished in 0.00179 seconds 3 examples, 0 failures
16. PROPRIEDADE
17. ∀ a, b → int, int (a + b) = (b + a)
18. ∀ a, b → int, int (a + b) = (b + a)
19. ∀ a, b → int, int (a + b) = (b + a)
20. ∀ a, b → int, int (a + b) = (b + a)
21. ∀ a, b → int, int (a + b) = (b + a)
22. ∀ a, b → int, int (a + b) = (b + a)
23. INVARIANTE
24. ∀ v → vector int each pair a, b in sort(v) a <= b
25. ∀ v → vector int each pair a, b in sort(v) a <= b
26. ∀ v → vector int each pair a, b in sort(v) a <= b
27. ∀ v → vector int each pair a, b in sort(v) a <= b
28. ∀ v → vector int each pair a, b in sort(v) a <= b
29. ∀ v → vector int each pair a, b in sort(v) a <= b
30. GERADORES
31. ∀ v → vector int each pair a, b in sort(v) a <= b
32. ∀ v → vector int each pair a, b in sort(v) a <= b v → [] v → [-1] v → [2 -1 1 -1 -2 5] v → [4] v → [7 9 -4 -4] …
33. CONTRA-EXEMPLO a.k.a. uma falha
34. [23 -17 8 -20 -35 -25 -22 10 11 -19 9 -3 -42 -33 -34 -11 7 -28 -5 38 39 -26 -29 42 0 -41 33 -35 19]
35. SHRINKING
36. !
37. !
38. [23 -17 8 -20 -35 -25 -22 10 11 -19 9 -3 -42 -33 -34 -11 7 -28 -5 38 39 -26 -29 42 0 -41 33 -35 19]
39. [42 0]
40. def sort(v) if v.include?(42) v else v.sort end end
41. COBERTURA
42. 01 def sort(v) 02 if v.include?(42) 03 v 04 else 05 v.sort 06 end 07 end
43. 01 def sort(v) 02 if v.include?(42) 03 v 04 else 05 v.sort 06 end 07 end v1 v2 v3 v4 …
44. PROPRIEDADE EXEMPLO
46. EXEMPLO in = “hello world!” out = “SGVsbG8gd29ybGQ=\n” expect(encode(in)).to eq(out)
47. PROPRIEDADE ∀ in → string in = decode(encode(in))
48. QuickCheck http://www.cse.chalmers.se/~rjmh/QuickCheck
49. Erlang QuickCheck http://www.quviq.com/products/erlang-quickcheck
50. Rantly https://github.com/hayeah/rantly
51. test.check https://github.com/clojure/test.check
52. …on Rails?
53. (+ clj-webdriver test.check)
54. Rails App Banco de Dados Testes Selenium* API webdriver JDBC UI
55. {:action :add-entry :via :ui :value 2995}
56. (defmulti dispatch! :action) ! (defmethod dispatch! :add-entry [action] (to base-url) (input-text “#entry_value" (str (:value action))) (submit "#entry_value"))
57. (defspec track-all-money-on-database 25 (for-all [actions gen-actions] (prepare-database! test-db) (dispatch-all! actions) (= (total-of actions) (total-recorded-in test-db))))
58. (defspec track-all-money-on-database 25 (for-all [actions gen-actions] (prepare-database! test-db) (dispatch-all! actions) (= (total-of actions) (total-recorded-in test-db))))
59. (defspec track-all-money-on-database 25 (for-all [actions gen-actions] (prepare-database! test-db) (dispatch-all! actions) (= (total-of actions) (total-recorded-in test-db))))
60. (defspec track-all-money-on-database 25 (for-all [actions gen-actions] (prepare-database! test-db) (dispatch-all! actions) (= (total-of actions) (total-recorded-in test-db))))
61. (defspec track-all-money-on-database 25 (for-all [actions gen-actions] (prepare-database! test-db) (dispatch-all! actions) (= (total-of actions) (total-recorded-in test-db))))
62. (defspec track-all-money-on-database 25 (for-all [actions gen-actions] (prepare-database! test-db) (dispatch-all! actions) (= (total-of actions) (total-recorded-in test-db))))
63. (defspec track-all-money-on-database 25 (for-all [actions gen-actions] (prepare-database! test-db) (dispatch-all! actions) (= (total-of actions) (total-recorded-in test-db))))
64. https://github.com/andrewhr/rails-test-check-example
65. Ashton Kemerling https://www.youtube.com/watch?v=HXGpBrmR70U
66. Ashton Kemerling https://www.youtube.com/watch?v=HXGpBrmR70U Também no Ruby Rogues #196 ;-)
67. Simulant https://github.com/Datomic/simulant
68. IDÉIAS LÁ FORA Wild, Wild West
69. Obrigado! Andrew @_andrewhr