Ruby: How to use global variables for a conditional debugger

Copyclass User

  after_save { byebug if $debug; nil }

  def lock
   self.locked = true
   save
  end

end

CopyRspec.describe User do

  let(:user) { create(:user) } 

  before do
   # Many users are created and saved in this hook, but we don't want the debugger to stop for them
   10.times { create(:user) }
  end

  it do
    # At this point we want to stop in the debugger for all following tests, when the :lock call runs into the after_save
    $debug = true
    expect { user.lock }.to change(user, :locked).from(false).to(true) 
  end

end