Enumerable RSpec matchers

enumerable_matchers.rb

module EnumerableMatchers
  # RSpec already lets you do this:
  #
  #   arr.should be_any {|item| item["foo"] == 2 }
  #
  # However, that's kind of unwieldy to say. So we add this matcher so we
  # can say one of these alternatives instead:
  #
  #   arr.should have_any {|item| item["foo"] == 2 }
  #   arr.should have_an  {|item| item["foo"] == 2 }
  #   arr.should have_a   {|hash| hash["foo"] == 2 }
  #
  # In English, that reads, "the array should have any item (an item, a hash)
  # whose 'foo' value equals 2".
  #
  def have_any(&block)
    HaveAny.new(block)
  end
  alias have_a have_any
  alias have_an have_any
 
  # RSpec already lets you do this:
  #
  #   arr.should be_all {|item| item["foo"] == 2 }
  #
  # However, that doesn't read very well for certain cases. For instance:
  #
  #   arr.should be_all {|item| item.is_a?(File) }
  #
  # This matcher lets you rewrite this as:
  #
  #   arr.should have_all {|item| item.is_a?(File) }
  #   arr.should all_have {|item| item.is_a?(File) }
  #
  # In English, that reads, "the array should have all items where each item
  # is a File", or "the array should all have an item where that item is a
  # File".
  #
  def have_all(&block)
    HaveAll.new(block)
  end
  alias all_have have_all

  class HaveAny
    def initialize(block)
      @block = block
    end
 
    def matches?(enum)
      enum.any?(&@block)
    end
 
    def failure_message_for_should
      "expected Enumerable to have an item, but it didn't"
    end
 
    def failure_message_for_should_not
      "expected Enumerable to not have an item, but it did"
    end
 
    def description
      "should have an item"
    end
  end
  
  class HaveAll
    def initialize(block)
      @block = block
    end
 
    def matches?(enum)
      enum.all?(&@block)
    end
 
    def failure_message_for_should
      "expected for all of the items to match a condition, but one of them didn't"
    end
 
    def failure_message_for_should_not
      "expected for none of the items to match a condition, but one of them did"
    end
 
    def description
      "should all match a condition"
    end
  end
end

RSpec.configure do |c|
  c.include(EnumerableMatchers)
end