Simple Rspec example

post.rb

class Post

  def initialize(attributes = {})
    @attributes = attributes
  end

  def publishable?
    @attributes[:approved]
  end

end

post_spec.rb

describe Post do

  context "when it's not approved" do
    subject { Post.new(:approved => false) }
    it { should_not be_publishable }
  end

  context "when it's approved" do
    subject { Post.new(:approved => true) }
    it { should be_publishable }
  end

end