Testing Gone Right

Mock is not a 4 letter word
Fast tests. Really Fast.
Rails Models

Transcript

1. Testing Gone Right from RubyConf 2011 and others @jwo - Jesse Wolgamott
2. What We’ll Talk Abouts • Mock is not a 4 letter word • Fast tests. Really Fast. • Rails Models
3. Mock is not a 4 letter word
4. Mocks • Mocks are not stubs • Mocks assert Messages • Assert on state => Stubbing • Assert on messages => Mocking
5. Ruby + OOP + Mock • is goood • Objects should tell objects to do things • (Tell don’t ask) • You tell to do things using messages
6. Mock Roles • Instead of mocking objects, try to mock roles • Wanting to mock concrete objects is a design smell
7. Example • Restaurant system reserves tables • Instead of your interface talking to a ReservationService: • Talk to ReservationInterfaceHandler
8. Message Example class ReservationInterface def initialize(handler) @handler = handler end def select_table(table) @table = table end def submit_request @handler.reserve(@table) end end
9. And to Spec it describe ReservationInterface do let(:table){something_interesting_here} it "should tell the handler to reserve a table" do handler = double('reservation_handler') handler.should_receive(:reserve).with(table) machine = ReservationInterface.new(handler) machine.select_table(table) machine.submit_request end
10. Watch Out!
11. On APIs • Only Mock Types you own • Don’t mock boundary objects • If you do, you’ll duplicate code -> CODE SMELL
12. Other Mock Smells • Having to setup more than 3 lines -- that’s a code smell • Mocking concrete objects -- that’s a code smell • When tests go brittle and developers declare mocks suck -- that’s a code smell
13. However • If you have a “standard” Rails app, programmed procedurally: • Mocks are not for you • If you encapulate your code. If you hide information (OOP). If you use messages: • Mocks are for you!
14. Mocks Don’t Suck • If your code is hard to test, you need better code • If you have a test that is HARD to setup, your class (or test) is doing too much • If you see tests with uber-mocks, the answer is not to delete mocks. It’s to isolate your tests
15. Fast Rails Tests
16. Out of the Box • Most Rails apps start as CRUD apps • Tests start fast-ish • Like a frog, we don’t notice the increase
17. “fast” tests • Tests should run in under a second • The entire rspec test suite
18. How? • Don’t load rails
19. Example Spec Run Time Real Time With Rails Without Rails .07 s 8.1 s 0.0007 s .8 s
20. Avoid Factories • Instead, extract your code to classes with one single responsibility • Rather than knowing everything about your object • Or, load methods via modules
21. Rails Models • Are Fat. • Wait, isn’t that good? • It’s better than controller logic • But no.
22. What then? • Your models can have validations • Call out to policy or decision classes for business logic • Use Ruby Classes • Use Presenters
23. Example • Example of building a burrito that is delicious, and can know it’s delicious • In Isolation: https://gist.github.com/1281093 • Using Modules: https://gist.github.com/ 1281064
24. Credits Why you don’t get mock objects @gregmoeck Your tests are lying to you @chrismdp Fast Rails talk at gogoruco 2011 @coreyhaines Testing in Isolation. destroyalldoftware.com @garybernhardt