Excellent, thanks for this!

I've tracked it down to two categories, both of which could be our fault:

1. Calling FactoryGirl methods from within FG definitions. For example:

    FactoryGirl.define do
      factory :configuration, aliases: [:config] do
        log4r {{
          filename: generate(:file_path),
        }}

Will cause the warning, but:

    FactoryGirl.define do
      factory :configuration, aliases: [:config] do
        log4r {{
          filename: FactoryGirl.generate(:file_path),
        }}

will not.

2. Passing unexpected data. For example:

    let(:config) { build :config, test_save: attrs(:test_save_config) }

    before do
      SaveUtil.stubs(:expand_path)
        .with(config.test_save.repo)
        .returns config.test_save.repo
    end

But the `:config` factory does not have a `test_save` attribute.

Hey @joshuaclayton and @jferris , do you have any thoughts here? It seems like (1) would benefit from a null object, and (2) isn't supposed to work anyway?