diff --git a/backend/.rspec b/backend/.rspec
new file mode 100644
index 0000000..c99d2e7
--- /dev/null
+++ b/backend/.rspec
@@ -0,0 +1 @@
+--require spec_helper
diff --git a/backend/Gemfile b/backend/Gemfile
index 303b937..4853e44 100644
--- a/backend/Gemfile
+++ b/backend/Gemfile
@@ -65,3 +65,5 @@ gem 'dotenv-rails'
 gem 'whenever', require: false
 
 gem 'discard'
+
+gem "rspec-rails", "~> 8.0", :groups => [:development, :test]
diff --git a/backend/Gemfile.lock b/backend/Gemfile.lock
index 2c08f92..1746b8c 100644
--- a/backend/Gemfile.lock
+++ b/backend/Gemfile.lock
@@ -298,6 +298,23 @@ GEM
       io-console (~> 0.5)
     rexml (3.4.1)
     rouge (3.30.0)
+    rspec-core (3.13.6)
+      rspec-support (~> 3.13.0)
+    rspec-expectations (3.13.5)
+      diff-lcs (>= 1.2.0, < 2.0)
+      rspec-support (~> 3.13.0)
+    rspec-mocks (3.13.7)
+      diff-lcs (>= 1.2.0, < 2.0)
+      rspec-support (~> 3.13.0)
+    rspec-rails (8.0.2)
+      actionpack (>= 7.2)
+      activesupport (>= 7.2)
+      railties (>= 7.2)
+      rspec-core (~> 3.13)
+      rspec-expectations (~> 3.13)
+      rspec-mocks (~> 3.13)
+      rspec-support (~> 3.13)
+    rspec-support (3.13.6)
     rss (0.3.1)
       rexml
     rubocop (1.75.6)
@@ -433,6 +450,7 @@ DEPENDENCIES
   puma (>= 5.0)
   rack-cors
   rails (~> 8.0.2)
+  rspec-rails (~> 8.0)
   rubocop-rails-omakase
   sprockets-rails
   sqlite3 (>= 2.1)
diff --git a/backend/app/controllers/ip_addresses_controller.rb b/backend/app/controllers/ip_addresses_controller.rb
deleted file mode 100644
index 5ede22a..0000000
--- a/backend/app/controllers/ip_addresses_controller.rb
+++ /dev/null
@@ -1,20 +0,0 @@
-class IpAddressesController < ApplicationController
-  def index
-    @ip_addresses = IpAddress.all
-
-    render json: @ip_addresses
-  end
-
-  def show
-    render json: @ip_address
-  end
-
-  def create
-  end
-
-  def update
-  end
-
-  def destroy
-  end
-end
diff --git a/backend/app/controllers/nico_tag_relation_controller.rb b/backend/app/controllers/nico_tag_relation_controller.rb
deleted file mode 100644
index 974f20e..0000000
--- a/backend/app/controllers/nico_tag_relation_controller.rb
+++ /dev/null
@@ -1,16 +0,0 @@
-class NicoTagRelationController < ApplicationController
-  def index
-  end
-
-  def show
-  end
-
-  def create
-  end
-
-  def update
-  end
-
-  def destroy
-  end
-end
diff --git a/backend/app/controllers/post_tags_controller.rb b/backend/app/controllers/post_tags_controller.rb
deleted file mode 100644
index 467074e..0000000
--- a/backend/app/controllers/post_tags_controller.rb
+++ /dev/null
@@ -1,16 +0,0 @@
-class PostTagsController < ApplicationController
-  def index
-  end
-
-  def show
-  end
-
-  def create
-  end
-
-  def update
-  end
-
-  def destroy
-  end
-end
diff --git a/backend/app/controllers/posts_controller.rb b/backend/app/controllers/posts_controller.rb
index a3a4538..dc10d90 100644
--- a/backend/app/controllers/posts_controller.rb
+++ b/backend/app/controllers/posts_controller.rb
@@ -81,7 +81,7 @@ class PostsController < ApplicationController
     # TODO: URL が正規のものがチェック，不正ならエラー
     # TODO: URL は必須にする（タイトルは省略可）．
     # TODO: サイトに応じて thumbnail_base 設定
-    title = params[:title]
+    title = params[:title].presence
     url = params[:url]
     thumbnail = params[:thumbnail]
     tag_names = params[:tags].to_s.split(' ')
@@ -122,7 +122,7 @@ class PostsController < ApplicationController
     return head :unauthorized unless current_user
     return head :forbidden unless current_user.member?
 
-    title = params[:title]
+    title = params[:title].presence
     tag_names = params[:tags].to_s.split(' ')
     original_created_from = params[:original_created_from]
     original_created_before = params[:original_created_before]
@@ -141,10 +141,6 @@ class PostsController < ApplicationController
     end
   end
 
-  # DELETE /posts/1
-  def destroy
-  end
-
   def changes
     id = params[:id]
     page = (params[:page].presence || 1).to_i
diff --git a/backend/app/controllers/settings_controller.rb b/backend/app/controllers/settings_controller.rb
deleted file mode 100644
index 379ca82..0000000
--- a/backend/app/controllers/settings_controller.rb
+++ /dev/null
@@ -1,16 +0,0 @@
-class SettingsController < ApplicationController
-  def index
-  end
-
-  def show
-  end
-
-  def create
-  end
-
-  def update
-  end
-
-  def destroy
-  end
-end
diff --git a/backend/app/controllers/tag_aliases_controller.rb b/backend/app/controllers/tag_aliases_controller.rb
deleted file mode 100644
index cbfd36f..0000000
--- a/backend/app/controllers/tag_aliases_controller.rb
+++ /dev/null
@@ -1,16 +0,0 @@
-class TagAliasesController < ApplicationController
-  def index
-  end
-
-  def show
-  end
-
-  def create
-  end
-
-  def update
-  end
-
-  def destroy
-  end
-end
diff --git a/backend/app/controllers/tags_controller.rb b/backend/app/controllers/tags_controller.rb
index 6597a43..7c1b250 100644
--- a/backend/app/controllers/tags_controller.rb
+++ b/backend/app/controllers/tags_controller.rb
@@ -34,13 +34,4 @@ class TagsController < ApplicationController
       head :not_found
     end
   end
-
-  def create
-  end
-
-  def update
-  end
-
-  def destroy
-  end
 end
diff --git a/backend/app/controllers/user_ips_controller.rb b/backend/app/controllers/user_ips_controller.rb
deleted file mode 100644
index c02396b..0000000
--- a/backend/app/controllers/user_ips_controller.rb
+++ /dev/null
@@ -1,16 +0,0 @@
-class UserIpsController < ApplicationController
-  def index
-  end
-
-  def show
-  end
-
-  def create
-  end
-
-  def update
-  end
-
-  def destroy
-  end
-end
diff --git a/backend/app/controllers/user_post_views_controller.rb b/backend/app/controllers/user_post_views_controller.rb
deleted file mode 100644
index 2bcefcd..0000000
--- a/backend/app/controllers/user_post_views_controller.rb
+++ /dev/null
@@ -1,16 +0,0 @@
-class UserPostViewsController < ApplicationController
-  def index
-  end
-
-  def show
-  end
-
-  def create
-  end
-
-  def update
-  end
-
-  def destroy
-  end
-end
diff --git a/backend/config/routes.rb b/backend/config/routes.rb
index 206d1a6..c7afe8f 100644
--- a/backend/config/routes.rb
+++ b/backend/config/routes.rb
@@ -1,7 +1,7 @@
 Rails.application.routes.draw do
   resources :nico_tags, path: 'tags/nico', only: [:index, :update]
 
-  resources :tags do
+  resources :tags, only: [:index, :show] do
     collection do
       get :autocomplete
       get 'name/:name', action: :show_by_name
@@ -30,7 +30,7 @@ Rails.application.routes.draw do
     end
   end
 
-  resources :posts do
+  resources :posts, only: [:index, :show, :create, :update] do
     collection do
       get :random
       get :changes
@@ -49,12 +49,4 @@ Rails.application.routes.draw do
       post 'code/renew', action: :renew
     end
   end
-
-  resources :ip_addresses
-  resources :nico_tag_relations
-  resources :post_tags
-  resources :settings
-  resources :tag_aliases
-  resources :user_ips
-  resources :user_post_views
 end
diff --git a/backend/db/migrate/20260107034300_make_title_nullable_in_posts.rb b/backend/db/migrate/20260107034300_make_title_nullable_in_posts.rb
new file mode 100644
index 0000000..80e6858
--- /dev/null
+++ b/backend/db/migrate/20260107034300_make_title_nullable_in_posts.rb
@@ -0,0 +1,28 @@
+class MakeTitleNullableInPosts < ActiveRecord::Migration[7.0]
+  def up
+    change_column_null :posts, :title, true
+
+    execute <<~SQL
+      UPDATE
+        posts
+      SET
+        title = NULL
+      WHERE
+        title = ''
+    SQL
+  end
+
+  def down
+    execute <<~SQL
+      UPDATE
+        posts
+      SET
+        title = ''
+      WHERE
+        title IS NULL
+    SQL
+
+    change_column_null :posts, :title, false
+  end
+end
+
diff --git a/backend/db/schema.rb b/backend/db/schema.rb
index 697bd8f..94e40d6 100644
--- a/backend/db/schema.rb
+++ b/backend/db/schema.rb
@@ -10,7 +10,7 @@
 #
 # It's strongly recommended that you check this file into your version control system.
 
-ActiveRecord::Schema[8.0].define(version: 2025_12_30_143400) do
+ActiveRecord::Schema[8.0].define(version: 2026_01_07_034300) do
   create_table "active_storage_attachments", charset: "utf8mb4", collation: "utf8mb4_0900_ai_ci", force: :cascade do |t|
     t.string "name", null: false
     t.string "record_type", null: false
@@ -84,7 +84,7 @@ ActiveRecord::Schema[8.0].define(version: 2025_12_30_143400) do
   end
 
   create_table "posts", charset: "utf8mb4", collation: "utf8mb4_0900_ai_ci", force: :cascade do |t|
-    t.string "title", null: false
+    t.string "title"
     t.string "url", limit: 2000, null: false
     t.string "thumbnail_base", limit: 2000
     t.bigint "parent_id"
diff --git a/backend/spec/rails_helper.rb b/backend/spec/rails_helper.rb
new file mode 100644
index 0000000..829cb4a
--- /dev/null
+++ b/backend/spec/rails_helper.rb
@@ -0,0 +1,77 @@
+# This file is copied to spec/ when you run 'rails generate rspec:install'
+require 'spec_helper'
+ENV['RAILS_ENV'] ||= 'test'
+require_relative '../config/environment'
+# Prevent database truncation if the environment is production
+abort("The Rails environment is running in production mode!") if Rails.env.production?
+# Uncomment the line below in case you have `--require rails_helper` in the `.rspec` file
+# that will avoid rails generators crashing because migrations haven't been run yet
+# return unless Rails.env.test?
+require 'rspec/rails'
+# Add additional requires below this line. Rails is not loaded until this point!
+
+# Requires supporting ruby files with custom matchers and macros, etc, in
+# spec/support/ and its subdirectories. Files matching `spec/**/*_spec.rb` are
+# run as spec files by default. This means that files in spec/support that end
+# in _spec.rb will both be required and run as specs, causing the specs to be
+# run twice. It is recommended that you do not name files matching this glob to
+# end with _spec.rb. You can configure this pattern with the --pattern
+# option on the command line or in ~/.rspec, .rspec or `.rspec-local`.
+#
+# The following line is provided for convenience purposes. It has the downside
+# of increasing the boot-up time by auto-requiring all files in the support
+# directory. Alternatively, in the individual `*_spec.rb` files, manually
+# require only the support files necessary.
+#
+# Rails.root.glob('spec/support/**/*.rb').sort_by(&:to_s).each { |f| require f }
+
+# Ensures that the test database schema matches the current schema file.
+# If there are pending migrations it will invoke `db:test:prepare` to
+# recreate the test database by loading the schema.
+# If you are not using ActiveRecord, you can remove these lines.
+begin
+  ActiveRecord::Migration.maintain_test_schema!
+rescue ActiveRecord::PendingMigrationError => e
+  abort e.to_s.strip
+end
+Dir[Rails.root.join('spec/support/**/*.rb')].each do |f|
+  require f
+end
+RSpec.configure do |config|
+  config.include TestRecords
+
+  # Remove this line if you're not using ActiveRecord or ActiveRecord fixtures
+  config.fixture_paths = [
+    Rails.root.join('spec/fixtures')
+  ]
+
+  # If you're not using ActiveRecord, or you'd prefer not to run each of your
+  # examples within a transaction, remove the following line or assign false
+  # instead of true.
+  config.use_transactional_fixtures = true
+
+  # You can uncomment this line to turn off ActiveRecord support entirely.
+  # config.use_active_record = false
+
+  # RSpec Rails uses metadata to mix in different behaviours to your tests,
+  # for example enabling you to call `get` and `post` in request specs. e.g.:
+  #
+  #     RSpec.describe UsersController, type: :request do
+  #       # ...
+  #     end
+  #
+  # The different available types are documented in the features, such as in
+  # https://rspec.info/features/8-0/rspec-rails
+  #
+  # You can also this infer these behaviours automatically by location, e.g.
+  # /spec/models would pull in the same behaviour as `type: :model` but this
+  # behaviour is considered legacy and will be removed in a future version.
+  #
+  # To enable this behaviour uncomment the line below.
+  # config.infer_spec_type_from_file_location!
+
+  # Filter lines from Rails gems in backtraces.
+  config.filter_rails_from_backtrace!
+  # arbitrary gems may also be filtered via:
+  # config.filter_gems_from_backtrace("gem name")
+end
diff --git a/backend/spec/requests/posts_spec.rb b/backend/spec/requests/posts_spec.rb
new file mode 100644
index 0000000..5b18521
--- /dev/null
+++ b/backend/spec/requests/posts_spec.rb
@@ -0,0 +1,30 @@
+require 'rails_helper'
+
+
+RSpec.describe 'Posts API', type: :request do
+  describe 'GET /posts' do
+    it 'returns tags with name in JSON' do
+      tn = TagName.create!(name: 'gen:spec_tag')
+      tag = Tag.create!(tag_name: tn, category: 'general')
+
+      post = Post.create!(title: 'spec post', url: 'https://example.com/spec')
+      PostTag.create!(post: post, tag: tag)
+
+      get '/posts'
+
+      expect(response).to have_http_status(:ok)
+
+      json = JSON.parse(response.body)
+      expect(json).to have_key('posts')
+      expect(json['posts']).to be_a(Array)
+      expect(json['posts']).not_to be_empty
+
+      tags = json['posts'][0]['tags']
+      expect(tags).to be_a(Array)
+      expect(tags).not_to be_empty
+
+      expect(tags[0]).to have_key('name')
+      expect(tags[0]['name']).to eq('gen:spec_tag')
+    end
+  end
+end
diff --git a/backend/spec/requests/tags_spec.rb b/backend/spec/requests/tags_spec.rb
new file mode 100644
index 0000000..deb10f5
--- /dev/null
+++ b/backend/spec/requests/tags_spec.rb
@@ -0,0 +1,48 @@
+require 'cgi'
+require 'rails_helper'
+
+
+RSpec.describe 'Tags API', type: :request do
+  let!(:tn) { TagName.create!(name: 'spec_tag') }
+  let!(:tag) { Tag.create!(tag_name: tn, category: 'general') }
+
+  describe 'GET /tags' do
+    it 'returns tags with name' do
+      get '/tags'
+
+      expect(response).to have_http_status(:ok)
+      json = JSON.parse(response.body)
+
+      expect(json).to be_a(Array)
+      expect(json).not_to be_empty
+      expect(json[0]).to have_key('name')
+      expect(json.map { |t| t['name'] }).to include('spec_tag')
+    end
+  end
+
+  describe 'GET /tags/autocomplete' do
+    it 'returns matching tags by q' do
+      get '/tags/autocomplete', params: { q: 'spec' }
+
+      expect(response).to have_http_status(:ok)
+      json = JSON.parse(response.body)
+
+      expect(json).to be_a(Array)
+      expect(json.map { |t| t['name'] }).to include('spec_tag')
+    end
+  end
+
+  describe 'GET /tags/name/:name' do
+    it 'returns tag by name' do
+      get "/tags/name/#{ CGI.escape('spec_tag') }"
+
+      expect(response).to have_http_status(:ok)
+      json = JSON.parse(response.body)
+
+      expect(json).to have_key('id')
+      expect(json).to have_key('name')
+      expect(json['id']).to eq(tag.id)
+      expect(json['name']).to eq('spec_tag')
+    end
+  end
+end
diff --git a/backend/spec/requests/wiki_spec.rb b/backend/spec/requests/wiki_spec.rb
new file mode 100644
index 0000000..7a874c6
--- /dev/null
+++ b/backend/spec/requests/wiki_spec.rb
@@ -0,0 +1,42 @@
+require 'cgi'
+require 'rails_helper'
+require 'securerandom'
+
+
+RSpec.describe 'Wiki API', type: :request do
+  let!(:user) { create_user_for_wiki! }
+
+  let!(:tn) { TagName.create!(name: 'spec_wiki_title') }
+  let!(:page) do
+    WikiPage.create!(tag_name: tn, created_user: user, updated_user: user)
+  end
+
+  describe 'GET /wiki' do
+    it 'returns wiki pages with title' do
+      get '/wiki'
+
+      expect(response).to have_http_status(:ok)
+      json = JSON.parse(response.body)
+
+      expect(json).to be_a(Array)
+      expect(json).not_to be_empty
+
+      expect(json[0]).to have_key('title')
+      expect(json.map { |p| p['title'] }).to include('spec_wiki_title')
+    end
+  end
+
+  describe 'GET /wiki/title/:title' do
+    it 'returns wiki page by title' do
+      get "/wiki/title/#{CGI.escape('spec_wiki_title')}"
+
+      expect(response).to have_http_status(:ok)
+      json = JSON.parse(response.body)
+
+      expect(json).to have_key('id')
+      expect(json).to have_key('title')
+      expect(json['id']).to eq(page.id)
+      expect(json['title']).to eq('spec_wiki_title')
+    end
+  end
+end
diff --git a/backend/spec/spec_helper.rb b/backend/spec/spec_helper.rb
new file mode 100644
index 0000000..327b58e
--- /dev/null
+++ b/backend/spec/spec_helper.rb
@@ -0,0 +1,94 @@
+# This file was generated by the `rails generate rspec:install` command. Conventionally, all
+# specs live under a `spec` directory, which RSpec adds to the `$LOAD_PATH`.
+# The generated `.rspec` file contains `--require spec_helper` which will cause
+# this file to always be loaded, without a need to explicitly require it in any
+# files.
+#
+# Given that it is always loaded, you are encouraged to keep this file as
+# light-weight as possible. Requiring heavyweight dependencies from this file
+# will add to the boot time of your test suite on EVERY test run, even for an
+# individual file that may not need all of that loaded. Instead, consider making
+# a separate helper file that requires the additional dependencies and performs
+# the additional setup, and require it from the spec files that actually need
+# it.
+#
+# See https://rubydoc.info/gems/rspec-core/RSpec/Core/Configuration
+RSpec.configure do |config|
+  # rspec-expectations config goes here. You can use an alternate
+  # assertion/expectation library such as wrong or the stdlib/minitest
+  # assertions if you prefer.
+  config.expect_with :rspec do |expectations|
+    # This option will default to `true` in RSpec 4. It makes the `description`
+    # and `failure_message` of custom matchers include text for helper methods
+    # defined using `chain`, e.g.:
+    #     be_bigger_than(2).and_smaller_than(4).description
+    #     # => "be bigger than 2 and smaller than 4"
+    # ...rather than:
+    #     # => "be bigger than 2"
+    expectations.include_chain_clauses_in_custom_matcher_descriptions = true
+  end
+
+  # rspec-mocks config goes here. You can use an alternate test double
+  # library (such as bogus or mocha) by changing the `mock_with` option here.
+  config.mock_with :rspec do |mocks|
+    # Prevents you from mocking or stubbing a method that does not exist on
+    # a real object. This is generally recommended, and will default to
+    # `true` in RSpec 4.
+    mocks.verify_partial_doubles = true
+  end
+
+  # This option will default to `:apply_to_host_groups` in RSpec 4 (and will
+  # have no way to turn it off -- the option exists only for backwards
+  # compatibility in RSpec 3). It causes shared context metadata to be
+  # inherited by the metadata hash of host groups and examples, rather than
+  # triggering implicit auto-inclusion in groups with matching metadata.
+  config.shared_context_metadata_behavior = :apply_to_host_groups
+
+# The settings below are suggested to provide a good initial experience
+# with RSpec, but feel free to customize to your heart's content.
+=begin
+  # This allows you to limit a spec run to individual examples or groups
+  # you care about by tagging them with `:focus` metadata. When nothing
+  # is tagged with `:focus`, all examples get run. RSpec also provides
+  # aliases for `it`, `describe`, and `context` that include `:focus`
+  # metadata: `fit`, `fdescribe` and `fcontext`, respectively.
+  config.filter_run_when_matching :focus
+
+  # Allows RSpec to persist some state between runs in order to support
+  # the `--only-failures` and `--next-failure` CLI options. We recommend
+  # you configure your source control system to ignore this file.
+  config.example_status_persistence_file_path = "spec/examples.txt"
+
+  # Limits the available syntax to the non-monkey patched syntax that is
+  # recommended. For more details, see:
+  # https://rspec.info/features/3-12/rspec-core/configuration/zero-monkey-patching-mode/
+  config.disable_monkey_patching!
+
+  # Many RSpec users commonly either run the entire suite or an individual
+  # file, and it's useful to allow more verbose output when running an
+  # individual spec file.
+  if config.files_to_run.one?
+    # Use the documentation formatter for detailed output,
+    # unless a formatter has already been configured
+    # (e.g. via a command-line flag).
+    config.default_formatter = "doc"
+  end
+
+  # Print the 10 slowest examples and example groups at the
+  # end of the spec run, to help surface which specs are running
+  # particularly slow.
+  config.profile_examples = 10
+
+  # Run specs in random order to surface order dependencies. If you find an
+  # order dependency and want to debug it, you can fix the order by providing
+  # the seed, which is printed after each run.
+  #     --seed 1234
+  config.order = :random
+
+  # Seed global randomization in this process using the `--seed` CLI option.
+  # Setting this allows you to use `--seed` to deterministically reproduce
+  # test failures related to randomization by passing the same `--seed` value
+  # as the one that triggered the failure.
+  Kernel.srand config.seed
+=end
+end
diff --git a/backend/spec/support/test_records.rb b/backend/spec/support/test_records.rb
new file mode 100644
index 0000000..e85b65b
--- /dev/null
+++ b/backend/spec/support/test_records.rb
@@ -0,0 +1,8 @@
+module TestRecords
+  def create_member_user!
+    User.create!(name: 'spec user',
+                 inheritance_code: SecureRandom.hex(16),
+                 role: 'member',
+                 banned: false)
+  end
+end