Service objects as a way of testing Rails apps

@andrzejkrzywda @arkency

In love/hate relationship with Rails, since 2004

Service objects

The things you call from your controllers

Rails is not your app Your app is below controllers

Most of the things without HTTP

AddProductToCart ChangeAmount

CreateNewBlogPost PublishBlogPost

AssignTestToPupils CreateNewKlass CheckoutOrder LogTimeEntry

ChangeInsurancePolicy

http://blog.arkency.com/2014/02/rails-refactoring-the-aha-moments/

Things that “do” something

Query objects - read the system

ListOfOrders UserQuery

PupilsInKlass BlogPostsByAuthor

Reads are easy Commands are more

difficult

Rails-way is good for Reads

Rails-way is not ideal for Commands

Testing

System tests vs

Unit tests

Good tests tell a story

1. User adds a product to the cart 2. User looks at the cart to see the current total amount

3. User changes the amount 4. User goes to checkout

How to setup the state?

factory_girl

Service objects in tests

What makes a good unit?

Unit == a set of service objects

scenario == service objects

Wins?

hides implementation details

tests in sync with production code

Easy to write

Fast

Problems?

Tests are one layer below !

Easy to make mistakes when calling services from controllers

Not so easy to extract services from an existing,

legacy Rails codebase

Examples

http://blog.arkency.com/2014/06/setup-your-tests-with-services/

Thanks!