Added MessageBoard and message_board_spec

spec/message_board_spec.rb

@@ -0,0 +1,18 @@
+require 'rspec'
+require './train'
+describe MessageBoard do
+
+  let(:message_board) { MessageBoard.new }
+	let(:engineer) { Engineer.new(message_board) }
+	let(:conductor) { Conductor.new(message_board)}
+
+	it "should tell the engineer to slow down" do
+		message_board.should_receive(:slow_down!)
+		conductor.see_danger_coming!
+	end
+
+  it "should confirm to the conductor that it slowed down" do
+    message_board.should_receive(:confirm_slow_down)
+    engineer.slowing_down!
+  end
+end

train.rb

@@ -1,15 +1,27 @@
 class Conductor
 
-	attr_reader :engineer
+	attr_reader :message_board
 
-	def initialize(engineer)
-		@engineer = engineer
+	def initialize(message_board)
+    @message_board = message_board
 	end
 
 	def see_danger_coming!
-		engineer.slow_down!
+		message_board.slow_down!
 	end
 end
 
 class Engineer
-end
+  attr_reader :message_board
+  def initialize(message_board)
+    @message_board = message_board
+  end
+
+  def slowing_down!
+    message_board.confirm_slow_down
+  end
+end
+
+class MessageBoard
+
+end

train_spec.rb

@@ -10,4 +10,4 @@
 		conductor.see_danger_coming!
 	end
 
-end
+end