我正在尝试将 factory_girl 4.2.0 与 rspec 2.13.0 一起使用。首先，我将“factory_girl”添加到我的 Gemfile 并进行捆绑更新：
Using aasm (3.0.16)
Using i18n (0.6.4)
Using multi_json (1.6.1)
Using activesupport (3.2.12)
Using builder (3.0.4)
Using activemodel (3.2.12)
Using arel (3.0.2)
Using tzinfo (0.3.36)
Using activerecord (3.2.12)
Using active_record_inline_schema (0.6.0)
Using tins (0.7.1)
Using amatch (0.2.11)
Using coderay (1.0.9)
Using conversions (1.4.6)
Using fastercsv (1.5.5)
Using fixed_width-multibyte (0.2.3)
Using hash_digest (1.0.0)
Using nokogiri (1.5.6)
Using rubyzip (0.9.9)
Using ruby-ole (1.2.11.6)
Using spreadsheet (0.8.2)
Using roo (1.10.3)
Using unix_utils (0.0.15)
Using remote_table (2.1.0)
Using to_regexp (0.2.0)
Using errata (1.1.1)
Using posix-spawn (0.3.6)
Using upsert (1.1.7)
Using data_miner (2.4.1)
Using diff-lcs (1.2.1)
Using httpclient (2.3.3)
Using method_source (0.8.1)
Using pg (0.14.1)
Using pg-hstore (1.1.7)
Using slop (3.4.3)
Using pry (0.9.12)
Using rspec-core (2.13.0)
Using rspec-expectations (2.13.0)
Using rspec-mocks (2.13.0)
Using rspec (2.13.0)
Using umarket1-package (0.2.0)
Using bundler (1.3.1)
然后在我的 spec_helper.rb 我做：
require 'factory_girl'
但我收到此错误：
.rvm/gems/ruby-1.9.3-p327/gems/factory_girl-4.2.0/lib/factory_girl/evaluation.rb:5:in `<class:Evaluation>': uninitialized constant FactoryGirl::Evaluation::Observable (NameError)
在 factory_girl 之前我需要其他要求吗？