diff --git a/replace-type-code-with-module-extension/lib/after.rb b/replace-type-code-with-module-extension/lib/after.rb
index e69de29..c82eea4 100644
--- a/replace-type-code-with-module-extension/lib/after.rb
+++ b/replace-type-code-with-module-extension/lib/after.rb
@@ -0,0 +1,37 @@
+class Employee
+  def initialize(type: :regular)
+    @type = type
+  end
+
+  def base_salary
+    500.0
+  end
+
+  def salary
+    base_salary + bonus
+  end
+
+  def self.build(type: :regular)
+    instance = new
+    instance.extend const_get(type.capitalize)
+  end
+
+end
+
+module Regular
+  def bonus
+    0
+  end
+end
+
+module Manager
+  def bonus
+    800
+  end
+end
+
+module Boss
+  def bonus
+    1500
+  end
+end
diff --git a/replace-type-code-with-module-extension/lib/before.rb b/replace-type-code-with-module-extension/lib/before.rb
index e69de29..20b81b5 100644
--- a/replace-type-code-with-module-extension/lib/before.rb
+++ b/replace-type-code-with-module-extension/lib/before.rb
@@ -0,0 +1,28 @@
+class Employee
+  def initialize(type: :regular)
+    @type = type
+  end
+
+  def base_salary
+    500.0
+  end
+
+  def salary
+    base_salary + bonus
+  end
+
+  private
+
+  def self.build(type: :regular)
+    new type: type
+  end
+
+  def bonus
+    value = case @type
+      when :regular then 0
+      when :boss    then 1500.0
+      when :manager then 800.0
+    end
+  end
+
+end
diff --git a/replace-type-code-with-module-extension/test/test.rb b/replace-type-code-with-module-extension/test/test.rb
index a8f6974..4b3a8ff 100644
--- a/replace-type-code-with-module-extension/test/test.rb
+++ b/replace-type-code-with-module-extension/test/test.rb
@@ -3,3 +3,22 @@
 
 require 'before' if ENV["BEFORE"]
 require 'after' unless ENV["BEFORE"]
+
+describe Employee do
+  describe "a regular one" do
+    it "has a salary" do
+      Employee.build.salary.must_equal 500.0
+    end
+  end
+
+  describe "a boss" do
+    it "has a salary" do
+      Employee.build(type: :boss).salary.must_equal 2000.0
+    end
+  end
+  describe "a manager" do
+    it "has a salary" do
+      Employee.build(type: :manager).salary.must_equal 1300.0
+    end
+  end
+end