Testing Shared Modules and ActiveSupport Concerns

Shared behavior

Often multiple models in the application share some common feature set.

For example, we may have multiple object types that can be:

• Purchased
• Tagged
• Commented on

We can use standard Ruby classes and modules for this shared behavior. If the shared behavior has both class and instance methods, Rails provides ActiveSupport::Concern, which allows us to easily use a common pattern to mix multiple kinds of behavior from one module.

Testing shared behavior

Testing this shared behavior can be a challenge. We don’t want to rewrite the shared behavior specs for each class that shares the mixed-in module. Simultaneously, if the shared feature depends on data being available in each class, that dependency is ...