A demo of some code I wrote to ensure cached values were being flushed appropriately.

test_caching.rb

# in spec_helper.rb

# Verify that the cache_busters bust the cache of the given method.
# 
# * method is the name of the method we are testing (for RSpec output)
# * cache_busters is a hash of labels => procs which should result in
#                 in the cache being flushed
#
# Please set these variables in specs which will be using this function:
#   @cached_function : a proc which executes the code to populate the cache
#   @key : a proc which returns the relevant cache key
#   @args : an array which will be used as the arguments to each of the cache
#           buster functions when they are called
def test_caching(method, cache_busters)

  describe "caching -" do
    
    before { @cached_function.call }
    
    it "should get cached" do
      Rails.cache.exist?(@key.call).should be_true
    end

    cache_busters.each do |label, f|
      it "should flush the cache after #{label}" do
        f.call(*@args)
        Rails.cache.exist?(@key.call).should be_false
      end          
    end
  end
end   


# Example spec, in any spec file
describe "attributed" do
  
  before do
    user = Factory(:user)
    conversation = user.conversations.create!
    @cached_function = -> { user.attributed }
    @key = -> { user.get_cache_key(:attributed) }
    @args = [conversation]        
  end
  
  cache_busters = {
    "deleting a participant" => ->(*args) {
      args[0].participants[0].destroy
    },
    "creating a new participant" => ->(*args) { 
      args[0].participants.create!
    },
    "updating a participant" => ->(*args) { 
      args[0].participants[0].update_attributes! :username => "new name"
    }
  }
  
  test_caching :attributed, cache_busters
  
end

# Runs the following specs...
#   attributed caching - should get cached
#   attributed caching - should flush the cache after creating a new participant
#   attributed caching - should flush the cache after deleting a participant
#   attributed caching - should flush the cache after updating a participant