a simple rspec

ex3.rb

module RSpec
  module DescribeExampleMethods
    def initialize(before_method, let_method)
      self.class.send(:define_method, :before_it) do |*args|
        before_method.call
      end

      self.class.send(:define_method, :let_method) do |*args|
        let_method.call
      end
    end

    def let(shortcut, &blk)
      define_singleton_method(shortcut, &blk)
    end

    def before(&blk)
      p = method(:before_it).to_proc.dup
      define_singleton_method(:before_it) do
        p.call
        blk.call
      end
    end

    def describe(msg, &blk)
      ::RSpec::DescribeExample.new(method(:before_it).to_proc, method(:let_it).to_proc).instance_eval(&blk)
    end

    def before_it

    end

    def let_it

    end

    def it(&blk)
      ::RSpec::it_examples << ::RSpec::ItExample.new(method(:before_it), method(:let_it), &blk)
    end
  end
end

module RSpec
  class ItExample
    def initialize(before_method, let_method, &blk)
      @before_method = before_method
      @let_method = let_method
      @blk = blk
    end

    def run
      @before_method.call
      @let_method.call
      @blk.call
    end
  end

  class << self
    attr_accessor :it_examples

    def it_examples
      @it_examples.flatten! if defined?(@it_examples) and @it_examples.respond_to?(:flatten!)
      @it_examples.uniq! if defined?(@it_examples) and @it_examples.respond_to?(:uniq!)
      @it_examples ||= []
    end
  end

  class DescribeExample
    include ::RSpec::DescribeExampleMethods
  end
end

module RSpec
  class << self
    include ::RSpec::DescribeExampleMethods
  end
end

module RSpec
  class C

  end

  describe "a msg" do
    #let(:c) { C.new }

    before do
      p '1 level before'
    end

    describe "2 level" do
      before do
        p '2 level before'
      end

      it do
        p '2 level it'
      end

    end

    it do
      p '1 level it'
    end
  end

end

RSpec.module_eval File.read(File.expand_path("../ex3_spec.rb", __FILE__))

RSpec.it_examples.each do |it_example|
  it_example.run
end

ex3_spec.rb

class C

end

describe "a msg" do
  #let(:c) { C.new }

  before do
    p '1 level before'
  end

  describe "2 level" do
    before do
      p '2 level before'
    end

    it do
      p '2 level it'
    end

  end

  it do
    p '1 level it'
  end
end