state? o_0

lib/car_production_line.rb

@@ -0,0 +1,11 @@
+class CarProductionLine
+  attr_accessor :state
+
+  def initialize
+    @state = ChassisState.new self
+  end
+
+  def install(part_to_install)
+    @state.next(part_to_install)
+  end
+end

lib/chassis_state.rb

@@ -0,0 +1,11 @@
+class ChassisState
+  def initialize(context)
+    @context = context
+  end
+
+  def next(part_to_install)
+    raise IlligalJumpError.new("State machine isn't being respected") unless part_to_install == :engine
+
+    @context.state = EngineState.new(@context)
+  end
+end

lib/engine_state.rb

@@ -0,0 +1,11 @@
+class EngineState
+  def initialize(context)
+    @context = context
+  end
+
+  def next(part_to_install)
+    raise IlligalJumpError.new("State machine isn't being respected") unless part_to_install == :hood
+
+    @context.state = HoodState.new(@context)
+  end
+end

lib/hood_state.rb

@@ -0,0 +1,11 @@
+class HoodState
+  def initialize(context)
+    @context = context
+  end
+
+  def next(part_to_install)
+    raise IlligalJumpError.new("State machine isn't being respected") unless part_to_install == :wheels
+
+    @context.state = WheelsState.new(@context)
+  end
+end

lib/illigal_jump_error.rb

@@ -0,0 +1,2 @@
+class IlligalJumpError < StandardError
+end

lib/wheels_state.rb

@@ -0,0 +1,9 @@
+class WheelsState
+  def initialize(context)
+    @context = context
+  end
+
+  def next(part_to_install)
+    raise NotImplementedError
+  end
+end

spec/anything_spec.rb

@@ -13,20 +13,20 @@
   let(:line) { CarProductionLine.new }
 
   it '1st step - chassis' do
-    expect{ line.state }.to be(ChassisState)
+    expect(line.state).to be_a(ChassisState)
   end
 
   it '2nd step - enging' do
     line.install :engine
 
-    expect{ line.state }.to be(EngineState)
+    expect(line.state).to be_a(EngineState)
   end
 
   it '3rd step - hood' do
     line.install :engine
     line.install :hood
 
-    expect{ line.state }.to be(HoodState)
+    expect(line.state).to be_a(HoodState)
   end
 
   it '3rd step - hood' do