Factory-girl create that bypasses my model validation

This isn't very specific to FactoryGirl, but you can always bypass validations when saving models via save(validate: false):

describe ".current" do
  let!(:current_group) { FactoryGirl.create(:group) }

  let!(:old_group) do
    g = FactoryGirl.build(:group, expiry: Time.now - 3.days)
    g.save(validate: false)
    g
 end
      
 specify { Group.current.should == [current_group] }
end

I prefer this solution from https://github.com/thoughtbot/factory_girl/issues/578.

Inside the factory:

trait :without_validations do
  to_create { |instance| instance.save(validate: false) }
end