I've done TDD wrong all the time

Transcript

1. © 2022 Thoughtworks I’ve done TDD wrong all the time 1
2. © 2022 Thoughtworks Test driven development 2 Write a failing test Make the test pass Refactor TDD
3. © 2022 Thoughtworks The benefit that was promised 3 Remove the fear of refactoring VS Unit test Mock
4. © 2022 Thoughtworks What are Unit tests and Mocks 4 Unit test Mock Mock Mock Class reference
5. © 2022 Thoughtworks Example 5
6. © 2022 Thoughtworks Bookstore 6 Has been asked to implement a ethical bookstore that that doesn't accept money It has two operation: • Withdraw a book • Deposit a book Withdraw a book it cost 2 credit points. If we have at least 5 credit we get a discount of 1 credit point. Deposit a book gives 1 credit point. If we have 10 or more credit points he will receive 1 credit point as extra bonus.
7. © 2022 Thoughtworks 7 TDD - 1° cycle 🔴
8. © 2022 Thoughtworks 8 TDD - 1° cycle 🟢
9. © 2022 Thoughtworks 9 TDD - 2° cycle 🔴
10. © 2022 Thoughtworks 10 TDD - 2° cycle 🟢
11. © 2022 Thoughtworks 11 TDD - 2° cycle 🟢
12. © 2022 Thoughtworks 12 TDD - 5° cycle 🟢
13. © 2022 Thoughtworks 13 TDD - 5° cycle 🟢
14. © 2022 Thoughtworks Book store - State pattern 14 1-2 Contributor member Community member 4-5 Affiliate member 9-10 Premium member Deposit Withdraw 0 +1 +1 -2 -1 +1 +2 -1
15. © 2022 Thoughtworks 15 Contributor State 🟢
16. © 2022 Thoughtworks 16 Community State 🟢
17. © 2022 Thoughtworks 17 Affiliate State 🟢
18. © 2022 Thoughtworks 18 Premium State 🟢
19. © 2022 Thoughtworks 19 Account 🟢
20. © 2022 Thoughtworks 20 Account 🔴
21. © 2022 Thoughtworks 21 Account 🟢
22. © 2022 Thoughtworks 22 What we have now • The tests don’t speak about “What” the application does but they are speaking about “How” • Tests are far to be a design tool • Fragile tests • For a few moment we gave up our safety-net
23. © 2022 Thoughtworks 23 I’ve made a mistake
24. © 2022 Thoughtworks 24 Account 🟢 State
25. © 2022 Thoughtworks Is TDD really helpful? 25 … or are we missing something?
26. © 2022 Thoughtworks What happened 26 Tests/mocks became an obstacle to the refactoring Write a failing test Make the test pass Refactor TDD We changed our code for some implementation details
27. © 2022 Thoughtworks What do we do when we write a test? 27 We are defining a contract that the code will fulfill
28. © 2022 Thoughtworks What do we do when we write a test? 28 We are defining a contract that the code will fulfill If it’s tight to implementation details it will easily breaks
29. © 2022 Thoughtworks What is a Unit test? 29 29 © 2021 Thoughtworks
30. © 2022 Thoughtworks Unit test Behaviour Not methods or classes 30
31. © 2022 Thoughtworks Tests should be coupled to the behavior of code and decoupled from the structure of code 31 Kent Beck
32. © 2022 Thoughtworks TDD is not really about test but more about behavior and requirement 32 TDD // BDD // ATDD // Module test
33. © 2022 Thoughtworks 33 33 Lots of confusion has been made around the name Unit test Coarse grained unit test Tests are coupled to the behaviours Fine grained unit test Tests are coupled to the implementation
34. © 2022 Thoughtworks The Test Diamond 34 Unit test Integration test UI test VS Fine Grained Unit test Coarse Grained Unit test Integration test UI test
35. © 2022 Thoughtworks 35 35 Combinatory logics Write tests for the logic condition All possible cases from the implementation point of view: • 3 + 1 = 4 (n+1) Write all possible scenario All possible cases from a requirement point of view are: • 2^3 = 9 (2^n) Give a free book if: A and (B or C) i.e. A = Deposit operation B = Is user’s birthday C = User has visited the shop 3 times in a week ⚠ trade-off
36. © 2022 Thoughtworks 36 TDD - Refactoring 🟢 If the requirement doesn’t change The test shouldn't change either
37. © 2022 Thoughtworks 37 What should we do when we write a test? Put yourself in the user’s shoes, tests should be executable specification Develop against an interface Outside-in
38. © 2022 Thoughtworks Are Mocks useless then? 38 38 © 2021 Thoughtworks
39. © 2022 Thoughtworks 39 Mock Mocks are useful for external dependency We should mock the infrastructure layer (through an adapter) i.e. DB, Kafka, HTTP call
40. © 2022 Thoughtworks 40 Mock Mocks are useful for isolate pieces of the application that have complex logics or isolate subdomains of our application ⚠ trade-off
41. © 2022 Thoughtworks I’ve found my balance 41 That’s how I’ve removed the fear of refactoring • Unit tests based on behaviours • Test against an interface • Do not mock logic, mock the infrastructure Your balance might be different 🤸
42. © 2022 Thoughtworks References 42 Books: Videos: TDD, Where Did It All Go Wrong Ian Cooper Outside-in diamond ◆ TDD Thomas Pierrain Automated tests: You won't find it in a book! Jacek Milewski TDD and Clean Architecture - Driven by Behaviour Valentina Cupać
43. © 2022 Thoughtworks 43 Luca Giuberti Senior Developer Consultant lucagiuberti @gix_lg Thank you
44. © 2022 Thoughtworks Questions? 44 44