Testing Named Scope

Tammer Saleh

We’re huge fans of NamedScope here at thoughtbot. It does wonders for finder reuse and clarity. Unfortunately, it also creates a large number of finders that all must be tested, where the old method may have only created one.

To help out with the testing of simple named_scope definitions, we added a helper to Shoulda, should_have_named_scope:

class User < ActiveRecord::Base
  named_scope :old,      :conditions => "age > 50"
  named_scope :eighteen, :conditions => { :age => 18 }
  named_scope :recent,   lambda {|count| { :limit => count } }

class UserTest < Test::Unit::TestCase
  should_have_named_scope :old,       :conditions => "age > 50"
  should_have_named_scope :eighteen,  :conditions => { :age => 18 }
  should_have_named_scope 'recent(5)', :limit => 5
  should_have_named_scope 'recent(1)', :limit => 1

Now for complex methods, where the options returned by the

has_finder are hairier than a simple limit or a single column condition, we would also write black box tests. But this helper is great for those simpler calls.