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Patch adds proxy-specific Factory.define options.
Patch adds a :singleton_on attribute to Factory.define; see README.rdoc for use-case information, but the basic gist is that when going through the create proxy, the value of the :singleton_on parameter is used on the generated instance to find a target, which is then searched for in the model the instance was created from. If an object is found, it is used instead of creating a new one, and then saved.
Tests added, pull request sent, working in real-world scenarios already.
We feel this need is adequately covered by the use of Rails' seed data feature.