custom_example_group.rb

require 'rubygems'
require 'spec'

class MyExampleGroup < Spec::ExampleGroup
  before(:each) do
    puts "in before(:each)"
    my_custom_method
  end

  class << self
  # available in groups
    def custom_example_group_method
      puts "hello from a custom example group class"
    end
  end

  # available in examples
  def custom_example_method
    puts "hello from a custom example group instance"
  end

  Spec::Example::ExampleGroupFactory.register :mine, self
end

describe "custom example group", :type => :mine do
  custom_example_group_method

  it "provides access to instance methods" do
    custom_example_method
  end
end

ivar_access_in_matcher.rb

require 'rubygems'
require 'spec'

module Spec
  module Matchers
    def equal_my_foo
      Matcher.new :equal_my_foo, @foo do |expected|
        match do |actual|
          actual.should == expected
        end
      end
    end
  end
end

describe "matcher" do
  it "should have access to an instance variable" do
    @foo = :bar
    :bar.should equal_my_foo
  end
end