factory_boy & behave

a talk on factory_boy and behave at Belfast Python Jan 2016

Transcript

1. FA C T O RY _ B O Y & B E H AV E S T E P H E N M C C U L L O U G H / / @ S W M C C / / P Y B E L FA S T / / J A N 2 0 1 6
2. A B O U T M E • @swmcc on the interwebs • Currently working at Shopkeep • Talk was written when I was working at MissionIQ
3. T H E V I R T U E O F T E S T I N G ? A L L A B O U T T E S T I N G
4. – S O M E O N E I U S E D T O W O R K F O R “I can’t sell tests, Stephen!”
5. W H AT I TA L K A B O U T • factory_boy - is a fixtures replacement based tool • behave - uses tests written in a natural language style, backed up by Python code
6. FA C T O RY _ B O Y
7. A U D I T P L U S • Mission IQ - auditplus. • ipad app + web ‘back-end’
8. A U D I T P L U S • Built using django. • First developed in May 2014 as a MVP. • Fully tested from the start. • Positive feedback lead to it becoming a full product.
9. W H Y U S E FA C T O RY _ B O Y ? • Audit didn’t use factory_boy from the start. • Happily used fixtures for over a year.
10. W H AT I S W R O N G W I T H F I X T U R E S ? • Easy to create. ‘manage.py dumpdata’. • Hard to read. • Hard to update. • Signal gets lost in the noise over time.
11. W H Y WA S A U D I T F E E L I N G T H E PA I N ? • The more complex the business logic the more complex the setup for a test case.
12. W H Y WA S A U D I T F E E L I N G T H E PA I N ? • Institutional knowledge required to write tests. • Fixture file was getting too big and a pain to edit. • Tests were getting slow to run. • Tests were getting too much of a pain to write.
13. I N T R O T O FA C T O RY _ B O Y • What it looks like in the wild
14. FA C T O RY _ B O Y • Can return default information. • Can override parameters if needed. • ‘Helper fields’ to aid in creating dynamic data. • This leads to a very potent testing framework.
15. S E Q U E N C E AT T R I B U T E S
16. L A Z Y AT T R I B U T E S
17. S C A F F O L D I N G
18. N I C E F E AT U R E S • traverse joins - using django ‘__’ syntax. 
 
 user = UserFactory(profile__wants_sms_reminders=False, • don’t save to the database.
 
 F.build() • default attribute as a dictionary.
 
 F.attributes() • override creation process.
 
 def create(self, **kwargs):

19. O R M S U P P O R T • Django • SQLAlchemy • Mogo • MogoMachine
20. B E H AV E
21. W H AT I S B E H AV E ? • behave is behaviour-driven development, Python style
22. – D A N N O R T H “BDD is a second-generation, outside–in, pull- based, multiple-stakeholder, multiple-scale, high- automation, agile methodology. It describes a cycle of interactions with well-defined outputs, resulting in the delivery of working, tested software that matters.”
23. – B E N N O R I C E “Behaviour testing allows you to test your application as a whole in such a way that all stakeholders can define and understand what is being tested.”
24. B D D ? • All stake holders (people that define, write and own the requirements) can understand what is being tested. • Much bigger avenue of agreement during the process. • Encourages thinking about the application in a natural, consistent language.
25. A L L O W E V E RY B O D Y T O W R I T E T E S T S • This is the ‘happy path’. • I have yet to see it happen. • I don’t think its necessarily a good thing to allow this.
26. R E Q U I R E M E N T S • Don’t define your tests from your requirements. • Then don’t define your application from your requirements. • You ‘just’ define your application from the tests. • And then tests ARE the requirements!
27. F E AT U R E S • As an [actor] (person/api consumer) • In order to [gain some benefit] • I want [a feature]
28. S C E N A R I O S • Given [a precondition] • When [an action] • Then [an expected outcome]
29. E X A M P L E O F A F E AT U R E
30. B I N D I N G • A ‘feature’ has to be binded to ‘something’ that can test it.
31. E X A M P L E O F A S T E P
32. G O O D A N D T H E B A D • As a concept I think BDD is good if in concert with other practises. • Everyone writing tests is a pipe dream. • The tooling is awful but if you keep your tests stupid it makes it easier.