Checks for all non-tenant models inside an app/models folder. Easy to run via rails console.

non_tenant_finder.rb

tenant_model_class = TenantModel
%x[ls app/models/].split("\n").each do |w|
  begin
    model = w[0...-3].camelize.constantize
    k = model
    while k != Object
      if k == ActiveRecord::Base
        unless model.include? tenant_model_class
          puts model
        end
      end
      k = k.superclass
    end
  rescue
  end
end