Gagnez en confiance dans vos tests - adapter contract testing

Vos tests sont au vert mais vous avez un bug en prod ?
Vous n'avez pas suffisamment confiance dans vos tests pour déployer en production ?
Vos tests vous ralentissent quand vous refactorez ?
L'intégration avec d'autres services sont source de bugs ?

Ces limitations peuvent venir de l’utilisation des mocks dans les tests. Mais comment les dépasser ?

Grâce à au contract testing et à l’architecture hexagonale, dans cette formation à forte composante pratique, vous apprendrez à tester l’intégration avec les services externes.
Cette approche permet d’obtenir des simulateurs à moindre coût qui se comportent exactement comme les services externes.
Cela se révèle être un formidable outil pour tester l’application dans son ensemble de manière plus explicite avec plus de confiance qu’en utilisant les mocks.

Transcript

1. Gagnez en con fi ance dans vos tests Adapter contract testing
2. Spiral journey
3. Spiral journey What did you say no to in order to attend this training ?
4. Spiral journey What did you say no to in order to attend this training ? According to you, what could Adapter Contract Testing be ?
5. Spiral journey What did you say no to in order to attend this training ? According to you, what could Adapter Contract Testing be ? From your experience, how contract testing may help you in your daily work ?
6. Spiral journey What did you say no to in order to attend this training ? According to you, what could Adapter Contract Testing be ? From your experience, how contract testing may help you in your daily work ? What is the big question you bring to this trining?
7. Meet your co-participants
8. Agenda • Hexagonal architecture • Adapter contract testing principle • TP1: contract test a database • State based vs interaction based testing • TP2 : contract test a read only provider • Le problème avec les mock • TP3 : use simulators to test & write domain application • Contract testing in the CI • Examples and REX • Contract testing in real life • Conclusion
9. Something to share before start ?
10. Pré-requis Cloner le projet github https://github.com/mathieucans/snail-race-kata Télécharger les images docker suivantes : docker run --rm -p 27017:27017 --name mongo_contract_testing -d mongo docker run --rm -d -p8000:8000 --name snail-race-server mathieucans/snail-race-server:latest
11. How do you feel confident with Hexagonal Architecture Test Driven Development ❓ ❓
12. Hexagonal Architecture • Origine : • https://alistair.cockburn.us/hexagonal-architecture/ • Autre nom : Ports & Adapters
13. Hexagonal Architecture Infrastructure Code Domain model use case use case Emailer Interface Repository Interface Primary port Secondary Port Email Service Data store MVC Controller MVC Controller Emailer Impl. Repository Impl. Is about domain and infrastructure
14. Hexagonal Architecture Infrastructure Code Domain model ✅ ⛔ Is about dependency
15. Hexagonal Architecture Necessary Essential Is about complexity
16. System test
17. Contract Contract test
18. Application test
19. Adapter contract testing
20. Adapter contract testing disclamer • Adapter contract testing is about : • domain & infrastructure • Hexagonal architecture • It’s not about : • µ-services • PACT (https://docs.pact.io/)
21. Test Real adapter Simulator Contract = running the same test Domain Interface Including anti-corruption layer External Service
22. DomainRepository Test (contract) Repository MongoDb Repository Fake Contract = running the same test DomainRepositoy (port) MongoDB
23. 🏁 Domain is about snail races 🏁 Register bets Select winners
24. Contract test BetRepositoryMongoDb
25. Adapter contract testing • Principes Adapter Domaine (Port) Infrastru cture Contract Test
26. Adapter contract testing • Exemple base de données BetRepository (Port) Contract Test Mongo BetRepositoryMongoDb
27. TP1.1 : Contract test a data base Cloner le projet github https://github.com/mathieucans/snail-race-kata Ouvrir le répertoire du langage de votre choix dans votre IDE Par exemple snail-race-bet/typescript/ pour travailler en typescript ⚠ Attention : ne pas utiliser le répertoire snail-race-server qui ne fait pas parti des exercices
28. A vous de jouer
29. TP1.2 Use contract test to write simulators Adapter Domaine (Port) Infrastructure Contract Test Fake Domaine (Port)
30. TP1.2 : Use contract test to write simulators BetRepositoryMongoDb BetRepository (Port) BetRepository Contract Mongo BetRepositoryFake
31. XUnit Jest / Jasmine Golang Tests location Abstract class Inside a function List of test methods Entrypoints Concrete class Spec fi le calling the function TestMain function
 running the list of methods How to use same test for both adapter and simulator
32. BetRepository Contract BetRepository MongoDb BetRepository Fake Only setup BetRepositoy (port) MongoDB BetRepository MongoDBTest BetRepository FakeTest All tests here Inherits Inherits
33. JS
34. State based vs interaction based testing
35. Interaction based SUT Test
36. Interaction based # SUT Test
37. State based SUT Test
38. Examples of adapters • Repository • Ex PersonRepository • File read/write wrapper • Message queue • External service wrapper • Ex Pdf extractor, email service …
39. Types of external dependencies Read - Registries - Pdf extraction - Weather Write - Emailing - Payments - Job launching Read - Write - Data stores - Identity pools - File systems
40. TP2 : Contract test a read only provider
41. TP2 Race result provider contract
42. TP2 Adapter contract testing • Contract test a read only provider RaceResultProvider (Port) Contract Test RaceResultProviderHttp snail- race-server RaceResultProviderFake
43. Anti corruption layer Domain side RaceResultProvider (Port) snail- race-server Infrastructure side SnailRaces SnailRace Podium Snail * 1 3
44. Use contract test to discover the api •Explore the endpoint with a unit test •Use the json response to create infrastructure types •Write a contract test that uses the desired port •Unit test the mapping (infra->domain) with pure unit tests •
45. Demo
46. Use contract test to discover the api •Explore the endpoint with a unit test •Use the json response to create infrastructure types •Write a contract test that uses the desired port •Unit test the mapping (infra->domain) with pure unit tests •
47. A vous de jouer
48. TP2 : Conclusion
49. Anticorruption layer testing • Static function transform(infraData): DomainData • Pure unit tests • Keep the anti-corruption layer in the infra
50. En quoi c’est mieux que les “mocks” ?
51. Test SUT Stub Spy Test SUT Fake / Simulator Other classes Setup Setup Veri fi cation Veri fi cation Testing with mocks Testing with fakes
52. Test SUT Fake / Simulator Other classes Setup Veri fi cation Read-Write depencency
53. Test SUT Fake / Simulator Other classes Setup Veri fi cation Domain Interface Read depencency
54. Test SUT Fake / Simulator Other classes Setup Veri fi cation Domain Interface Write depencency
55. Advantages with adapter and contract tests • The real deal • Easy to setup • Catches external bugs • Fast • No “mock bugs” • Easier to interact with the external dependency • Easy to change technology • Easy to change the contract
56. TP3 : Use simulators to write domain application
57. Use fakes to test domain
58. Domain rules The application can register bets • registering a bet is done by providing • gambler name • the 3 numbers of snails on the podium The application lists the winners according to last race ran. To win a bet : • The podium match exactly the race result • The bet has been registered at least 3 seconds before the race timestamp • A bet is valid only for the next race
59. TP3 : Correction
60. Anti-Corruption vs domain layer opportunities What’s the reach of the anti-corruption layer?
61. • Where is implemented the selection of the snails on the Podium ? RaceResultProvider (Port) SnailRaces SnailRace Podium Snail * 1 3 RaceResultProvider (Port) SnailRaces SnailRace Snail * 1 10 VS Anti-Corruption vs domain layer opportunities
62. • How do we ensure that we select the last race ? RaceResultProvider (Port) SnailRaces SnailRace Podium Snail * 1 3 VS RaceResultProvider (Port) SnailRace Podium Snail 1 3 Anti-Corruption vs domain layer opportunities
63. Anti-Corruption vs domain layer opportunities • Other examples : • What about snail number unicity in the podium ? • What about races with less than 3 snails ? • What about equal positions?
64. Annoyances with adapter tests • Availability • Speed • External changes? - and frequency • Cost of call • Accessible locally?
65. Contract tests in the CI • Put in a separate pipeline (possibly di ff erent triggers/periodicity) • Put in an optional pipeline/step • Use as uptime-bot • Extract as a library • Make them stable! • No CI
66. Examples and feedbacks
67. Use contract test for production metrics • Use exactly same test to generate metrics on production • Useful when traffic still small • Better diagnostic • OPS can monitor them
68. Example: gmail reply detection Gmail has no native way to check if an email has been replied to It can be implemented through threads Need to expose this to the domain 1. Discovered how thread works through contract tests 2. Use these tests to write a simulator like gmail 3. Very productive and con fi dent in implementing the domain logic
69. Example : api change Both simulators and contract test shave been written to consume orange mails The application was tested with simulators Need to change end point used to read mails in the adapter (QOS issue) 1. Write the adapter with the new end point 2. Check the behavior still works as the old one and the simulator 3. Integrate the new end point safely without change neither domain code nor domain tests
70. Example : bu Both simulators and contract test shave been written to consume orange mails The application was tested with simulators Need to change end point used to read mails in the adapter (QOS issue) 1. Write the adapter with the new end point 2. Check the behavior still works as the old one and the simulator 3. Integrate the new end point safely without change neither domain code nor domain tests
71. Example: remote fi le system (OneDrive) • Very slow, in particular for listing nested folders • There were around 15 methods on it • Having the fake made it very easy to implement a good caching system • As a result it was easy to implement both a persistent and an ephemeral caching system Storage OneDrive Slow
72. Example: public company registry • Getting info about companies • Problem: not really. Read-only but stable • Solution: keep the exact assertions • In retrospect: They changed sometimes, but not often. Our app Data.gouv
73. Example: data.entreprise.gouv • Getting (more) info about companies • Problem: Heteregenous data • Solution: Try ingesting big amounts of data as a test • Result: We discovered rare problems in dev as opposed to production Our app Data.gouv Heteregenous 
 data
74. Example: Android system • A js-app running on android, it has a chatty api with a native app. • Problem: complex and wrong mocking • Solution: build a simulator (without contract testing) • Gain: Reliable tests of the isolated js-app js app native app Complex 
 interactions
75. Example: Run tests on DB production • Warning : after the training • Running contract test in isolation as much as possible
76. What about real production code
77. Exercice: write contract test for your project • List the contract tests you’d write for one of your dependencies (only names) • Start implementing some tests on the real dependency, as if you were starting from scratch • Improve the interface (i.e. extract or refactor) • In particular no infra concerns should transpire • Transform it to a contract test
78. Quelques références • Contract Test - Martin Fowler • Testing Without Mocks - James Shore • Architecture Hexagonale : gestion de la complexité logicielle et de la dette technique - Julien Topçu
79. Con fi ance dans les 
 tests du domaine Tests de l’infra pertinents Migration de dépendance facile Refactorabilité 
 ++ 
 Contract
 Testing
80. Debrief
81. Vos feedbacks sont importants • Feedback qualitatif