memcached_value_change_spec.rb

# I'm interested in improvements or variations on doing this in rspec

# assuming we have an instance of ActiveSupport::Cache::MemCacheStore
# as the constant Mem and we want to check to see if a method changes
# the value for a particular key

# this comes into play in the first spec below...
class MemcachedValueFor
  def self.method_missing name, *args
    Mem.fetch(name)
  end
end

describe 'checking that a memcached value is changed' do
  before(:each) do
    # set our base value
    Mem.write('person_name', 'edna')
  end

  # this is the method we would be testing to ensure that it changes the
  # memcached key.
  def mystery_method
    Mem.write('person_name', 'ralph')    
  end

  # I like this syntax, but using a class w/ method_missing is pretty hacky
  it "should be testable via lambda / should change" do
    lambda{
      mystery_method
    }.should change(MemcachedValueFor, :person_name).to('ralph')
  end

  # now, this doesn't verify the final result, but do we really want to be
  # testing that MemCacheStore works here or just that it gets the message?
  # The spec will fail if #write is called more than once, so it should
  # cover the bases.
  it "should be testable with stubbing" do
    Mem.should_receive(:write).with("person_name", "ralph")
    mystery_method
  end
end