Can't get Flipper feature to enable for a group

Question

I'm using the Flipper gem on Rails. I'm trying the following, and finding it doesn't work:

Flipper.register(:admins) do |actor|
  actor.respond_to?(:is?) && actor.is?(:admin)
end

$flipper[:payments].disable
$flipper[:payments].enable $flipper.group(:admins)

Not only does that not work, but this doesn't work:

Flipper.register(:admins) do |actor|
  true
end

$flipper[:payments].disable
$flipper[:payments].enable $flipper.group(:admins)

This DOES work:

$flipper[:payments].disable
$flipper[:payments].enable

What could be the deal?

Answer 1

Turns out I needed to take the current user into account.

$flipper[:payments].enabled?               # doesn't work
$flipper[:payments].enabled?(current_user) # works