diff --git a/.gitignore b/.gitignore
index 07edafd..78919eb 100644
--- a/.gitignore
+++ b/.gitignore
@@ -17,6 +17,6 @@
 
 /bin/set-env.sh
 
-/coverage/*
+/coverage/.*
 
 *.bk
diff --git a/Guardfile b/Guardfile
index 4684d50..a503d81 100644
--- a/Guardfile
+++ b/Guardfile
@@ -1,4 +1,4 @@
-guard :rspec, spring: true do
+guard :rspec, all_after_pass: true, spring: true do
   watch(%r{^spec/.+_spec\.rb$})
   watch(%r{^lib/(.+)\.rb$})     { |m| "spec/lib/#{m[1]}_spec.rb" }
   watch('spec/spec_helper.rb')  { 'spec' }
@@ -11,7 +11,7 @@ guard :rspec, spring: true do
   watch('app/controllers/application_controller.rb')  { 'spec/controllers' }
 end
 
-guard :rubocop, cli: ['--rails', '--auto-correct'] do
+guard :rubocop, all_after_pass: true, cli: ['--rails', '--auto-correct'] do
   watch(%r{.+\.rb$})
   watch(%r{(?:.+/)?\.rubocop\.yml$}) { |m| File.dirname(m[0]) }
 end
diff --git a/app/controllers/posts_controller.rb b/app/controllers/posts_controller.rb
index 00c5ce3..2e6ebf3 100644
--- a/app/controllers/posts_controller.rb
+++ b/app/controllers/posts_controller.rb
@@ -1,5 +1,4 @@
 require 'nkf'
-require 'rv/mailer'
 
 class PostsController < ApplicationController
   before_action :set_post, only: [:show, :edit, :update, :destroy]
@@ -12,7 +11,7 @@ class PostsController < ApplicationController
   # GET /posts.json
   def index
     if params[:q].present?
-      @posts = Post.build_query(params).limit(10)
+      @posts = Post.search(params[:q]).limit(10)
     else
       @posts = Post.order(updated_at: :desc).limit(10)
     end
diff --git a/app/models/post.rb b/app/models/post.rb
index 9d3bffe..a85c56f 100644
--- a/app/models/post.rb
+++ b/app/models/post.rb
@@ -4,18 +4,15 @@ class Post < ActiveRecord::Base
   belongs_to :author, class_name: 'User'
 
   # Named scope
-
-  def self.build_query(params)
+  scope :search, (lambda do |query|
     _where_list = includes(:author, :tags)
 
     # Convert spaces to one space.
-    query_string = params[:q].gsub(/[\s　]+/, ' ')
-
-    query_list = query_string.split(' ')
+    query_list = query.gsub(/[\s　]+/, ' ').split(' ')
 
     query_list.each do |_query|
       case _query
-      when /^post:(.+)/
+      when /^id:(.+)/
         _where_list = _where_list.where('id = ?', Regexp.last_match[1])
       when /^title:(.+)/
         _where_list = _where_list.where('title LIKE ?', "%#{Regexp.last_match[1]}%")
@@ -34,7 +31,7 @@ def self.build_query(params)
     end
 
     _where_list
-  end
+  end)
 
   # generate forked post (not saved)
   def generate_fork(user)
diff --git a/app/views/partials/_app_header.html.erb b/app/views/partials/_app_header.html.erb
index 47d51a5..4fa239d 100644
--- a/app/views/partials/_app_header.html.erb
+++ b/app/views/partials/_app_header.html.erb
@@ -14,7 +14,7 @@
 
     <!-- Collect the nav links, forms, and other content for toggling -->
     <div class="collapse navbar-collapse" id="bs-example-navbar-collapse-1">
-      <form id="app-search-form" class="navbar-form navbar-left" role="search" action="<%= root_path %>">
+      <form id="app-search-form" class="navbar-form navbar-left" role="search" action="<%= posts_path %>">
         <div class="input-group">
           <input type="text" name="q" class="form-control" value="<%= params[:q] %>" placeholder="Search">
           <span class="input-group-btn">
diff --git a/coverage/.last_run.json b/coverage/.last_run.json
deleted file mode 100644
index fbf45e5..0000000
--- a/coverage/.last_run.json
+++ /dev/null
@@ -1,5 +0,0 @@
-{
-  "result": {
-    "covered_percent": 82.72
-  }
-}
diff --git a/spec/factories/posts.rb b/spec/factories/posts.rb
index f4e3d62..e8e16c8 100644
--- a/spec/factories/posts.rb
+++ b/spec/factories/posts.rb
@@ -1,6 +1,7 @@
 # Read about factories at https://github.com/thoughtbot/factory_girl
 
 FactoryGirl.define do
+
   factory :post do
     title 'sample title'
     body 'sample body'
@@ -12,5 +13,4 @@
 
   factory :post_tag do
   end
-
 end
diff --git a/spec/models/post_spec.rb b/spec/models/post_spec.rb
index d88f7a1..202e0c3 100644
--- a/spec/models/post_spec.rb
+++ b/spec/models/post_spec.rb
@@ -31,4 +31,52 @@
     end
   end
 
+  describe 'scope :search' do
+    before :each do
+      @alice = create(:alice)
+      @post1 = Post.create id: 1001, title: 'ruby rspec', body: 'This is first espec test: ruby'
+      @post2 = Post.create id: 1002, title: 'php test', body: 'PHP is very easy', author_id: @alice.id
+      @post3 = Post.create id: 1003, title: 'java java...', body: 'Java is not ruby...', updated_at: Time.new(1989, 2, 25, 5, 30, 0)
+      @tag_java = Tag.create(name: 'java')
+      @post3.tags << @tag_java
+    end
+
+    it 'by id' do
+      expect(Post.search('id:1001')).to have(1).items
+      expect(Post.search('id:1001')).to include(@post1)
+    end
+
+    it 'by title' do
+      expect(Post.search('title:ruby')).to have(1).items
+      expect(Post.search('title:ruby')).to include(@post1)
+    end
+
+    it 'by body' do
+      expect(Post.search('body:ruby')).to have(2).items
+      expect(Post.search('body:ruby')).to include(@post3)
+    end
+
+    it 'by @<author_name>' do
+      expect(Post.search('@Alice')).to have(1).items
+      expect(Post.search('@Alice')).to include(@post2)
+    end
+
+    it 'by #<tag_name>' do
+      expect(Post.search('#java')).to have(1).items
+      expect(Post.search('#java')).to include(@post3)
+    end
+
+    it 'by date' do
+      expect(Post.search('date:1989-2-25')).to have(1).items
+      expect(Post.search('date:1989-2-25')).to include(@post3)
+    end
+
+    it 'by else' do
+      expect(Post.search('ruby')).to have(2).items
+      expect(Post.search('ruby')).to include(@post1)
+      expect(Post.search('ruby')).to include(@post3)
+    end
+
+  end
+
 end