RSpec matcher for have_named_scope, extended to allow testing of procs - original at http://www.evolve.st/articles/11-testing-named-scope-with-rspec

image.rb

class Image < ActiveRecord::Base
  named_scope :allowed_for, lambda { |account| { :conditions => ["aws_is_public = ? OR account_id = ?", true, account.id] }}
end

image_spec.rb

describe Image do

  describe "named scopes" do

    it "should have a 'allowed_for' named scope where either 'aws_is_public' is true or 'account_id' matches the id for the passed in account" do
      Image.should have_named_scope(:allowed_for,
        lambda { |account| { :conditions => ["aws_is_public = ? OR account_id = ?", true, account.id] }},
        mock('Account', :id => 1))
    end

  end

end

named_scope_spec_helper.rb

module NamedScopeSpecHelper

  class HaveNamedScope  #:nodoc:

    def initialize(scope_name, options, proc_args=nil)
      @scope_name = scope_name.to_s
      @options    = options
      @proc_args  = proc_args
    end

    def matches?(klass)
      @klass = klass
      if @options.class == Proc
        @klass.send(@scope_name, *@proc_args).proxy_options.should === @options.call(*@proc_args)
      else
        @klass.send(@scope_name).proxy_options.should === @options
      end
      true
    end

    def failure_message
      "expected #{@klass} to define named scope '#{@scope_name}' with options #{@options.inspect}, but it didn't"
    end

    def negative_failure_message
      "expected #{@klass} to not define named scope '#{@scope_name}' with options #{@options.inspect}, but it did"
    end

  end

  def have_named_scope(scope_name, options, proc_args=nil)
    HaveNamedScope.new(scope_name, options, proc_args)
  end

end

spec_helper.rb

# Default spec_helper code left out for clarity

include NamedScopeSpecHelper