collection_matchers.rb

module CollectionMatchers
  # Use with any existing matcher
  # Example:
  #   posts.should all.be_published
  #   # Same as:
  #   posts.should_not be_empty
  #   posts.each { |post| post.should be_published }
  def all
    CollectionMatcher.new(self)
  end

  class CollectionMatcher
    def initialize(example)
      @example = example
    end

    def method_missing(matcher, *args, &block)
      @matcher = matcher
      @args    = args
      @block   = block
      self
    end

    def matches?(collection)
      if collection.nil? || collection.empty?
        @failure_message = "Can't test an empty collection"
        return false
      end

      collection.all? do |item|
        matcher = @example.send(@matcher, *@args, &@block)
        if matcher.matches?(item)
          @negative_failure_message = matcher.negative_failure_message
          true
        else
          @failure_message = matcher.failure_message
          false
        end
      end
    end

    attr_reader :failure_message, :negative_failure_message
  end
end