Move Project#create_from_todo to its own class

The point of this is to keep as many things out of the ActiveRecord
objects as possible and use them as just a thin database abstraction
layer.

app/controllers/todos_controller.rb

@@ -776,7 +776,7 @@ class TodosController < ApplicationController
 
   def convert_to_project
     todo = current_user.todos.find(params[:id])
-    @project = Project.create_from_todo(todo)
+    @project = ProjectFromTodo.new(todo).create
 
     if @project.valid?
       redirect_to project_url(@project)

app/models/project.rb

@@ -47,21 +47,6 @@ class Project < ActiveRecord::Base
     NullProject.new
   end
 
-  def self.create_from_todo(todo)
-    project = Project.new(:name => todo.description,
-                          :description => todo.notes,
-                          :default_context => todo.context)
-
-    project.user = todo.user
-
-    if project.valid?
-      todo.destroy
-      project.save!
-    end
-
-    project
-  end
-
   def hide_todos
     todos.each do |t|
       unless t.completed? || t.deferred?

lib/project_from_todo.rb

@@ -0,0 +1,27 @@
+class ProjectFromTodo
+  attr_reader :todo
+
+  def initialize(todo)
+    @todo = todo
+  end
+
+  def create
+    project = build_project
+
+    if project.valid?
+      todo.destroy
+      project.save!
+    end
+
+    project
+  end
+
+  def build_project
+    project = Project.new.tap do |p|
+      p.name = todo.description
+      p.description = todo.notes
+      p.default_context = todo.context
+      p.user = todo.user
+    end
+  end
+end

test/unit/project_from_todo_test.rb

@@ -0,0 +1,22 @@
+require_relative '../test_helper'
+require_relative '../../lib/project_from_todo'
+
+class ProjectFromTodoTest < ActiveSupport::TestCase
+  fixtures :todos
+
+  def test_create_project_from_valid_todo
+    todo = todos(:upgrade_rails)
+    project = ProjectFromTodo.new(todo).create
+    assert_equal project.name, todo.description
+    assert_equal project.description, todo.notes
+    assert_equal project.default_context, todo.context
+  end
+
+  def test_invalid_project_from_invalid_todo
+    todo = todos(:upgrade_rails)
+    todo.description = ""
+    project = ProjectFromTodo.new(todo).create
+    assert_not_nil project
+    assert_equal false, project.valid?
+  end
+end

test/unit/project_test.rb

@@ -167,14 +167,6 @@ class ProjectTest < ActiveSupport::TestCase
     assert_equal 3, @moremoney.todos.not_completed.count
   end
 
-  def test_convert_from_todo
-    todo = todos(:upgrade_rails)
-    project = Project.create_from_todo(todo)
-    assert_equal project.name, todo.description
-    assert_equal project.description, todo.notes
-    assert_equal project.default_context, todo.context
-  end
-
   def test_new_record_before_save
     assert !@timemachine.new_record_before_save?, "existing records should not be new_record"
     p = Project.where(:name => "I do not exist").first_or_create