bad.rb

require 'rspec/autorun'

module Stuff
  def authenticated_as
    puts "1: #{self.inspect}"
    context 'when there is stuff' do
      puts "2: #{self.inspect}"
      yield
    end
  end
end

RSpec.configure do |config|
  config.extend Stuff
end

describe "some stuff" do
  puts "0: #{self.inspect}"
  authenticated_as do
    puts "3: #{self.inspect}"
    it "should work" do
      true.should be_false
    end
  end
end

# output:
# src/tmp/rspec $ ruby test.rb
# 0: #<Class:0x007f9985b50150>
# 1: #<Class:0x007f9985b50150>
# 2: #<Class:0x007f9985b478c0>
# 3: #<Class:0x007f9985b50150>

good.rb

require 'rspec/autorun'

module Stuff
  def authenticated_as(&blk)
    puts "1: #{self.inspect}"
    context 'when there is stuff' do
      puts "2: #{self.inspect}"
      instance_eval(&blk)
    end
  end
end

RSpec.configure do |config|
  config.extend Stuff
end

describe "some stuff" do
  puts "0: #{self.inspect}"
  authenticated_as do
    puts "3: #{self.inspect}"
    it "should work" do
      true.should be_false
    end
  end
end

# output:
# src/tmp/rspec $ ruby test.rb
# 0: #<Class:0x007ff006350130>
# 1: #<Class:0x007ff006350130>
# 2: #<Class:0x007ff006347fa8>
# 3: #<Class:0x007ff006347fa8>