post.rb

class Post < ActiveRecord::Base
  validates_length_of :title, :minimum => 4
  
  def custom_method
    title.scan(/./).join(' ').upcase
  end
end

post_test.rb

require 'test_helper'

class PostTest < ActiveSupport::TestCase
  # setup do
  #   if Object.const_defined?(:Fixtures) && Fixtures.respond_to?(:reset_cache)
  #     Fixtures.reset_cache
  #   end
  # end
  
  should_ensure_length_at_least :title, 4
  
  def test_title
    p = Post.create :title => "test"
    assert_equal "test", p.reload.title
    
    # Method that is not an attribute
    assert_equal "T E S T", p.custom_method
    
    # Use fixtures
    assert_equal Post, posts(:one).class
    assert_equal "title from fixture", posts(:one).title
  end
  
  context "in shoulda context" do
    setup do
      @post = posts(:one)
    end
    
    should "respond to title" do
      assert_equal "title from fixture", @post.title
    end
  end
end