diff --git a/.github/workflows/test.yml b/.github/workflows/test.yml
index 93f926a..8d19321 100644
--- a/.github/workflows/test.yml
+++ b/.github/workflows/test.yml
@@ -21,6 +21,7 @@ jobs:
         ruby:
           - "3.3"
           - "3.4"
+          - "4.0"
 
     steps:
       - uses: actions/checkout@8e8c483db84b4bee98b60c0593521ed34d9990e8 # v6.0.1
@@ -34,7 +35,7 @@ jobs:
         run: |
           set -xe
           bundle config path vendor/bundle
-          bundle update --jobs $(nproc) --retry 3
+          bundle update --all --jobs $(nproc) --retry 3
 
       - run: sudo apt-get update
       - run: sudo apt-get install -y universal-ctags
@@ -65,7 +66,7 @@ jobs:
         run: |
           set -xe
           bundle config path vendor/bundle
-          bundle update --jobs $(nproc) --retry 3
+          bundle update --all --jobs $(nproc) --retry 3
 
       - run: bundle exec rake rubocop
 
@@ -92,7 +93,7 @@ jobs:
         run: |
           set -xe
           bundle config path vendor/bundle
-          bundle update --jobs $(nproc) --retry 3
+          bundle update --all --jobs $(nproc) --retry 3
 
       - run: bundle exec rake rbs:install
       - run: bundle exec rake rbs
@@ -105,6 +106,37 @@ jobs:
           status: ${{ job.status }}
           webhook-url: ${{ secrets.SLACK_WEBHOOK }}
 
+  yard:
+    runs-on: ubuntu-latest
+
+    steps:
+      - uses: actions/checkout@8e8c483db84b4bee98b60c0593521ed34d9990e8 # v6.0.1
+
+      - uses: ruby/setup-ruby@ae195bbe749a7cef685ac729197124a48305c1cb # v1.276.0
+        with:
+          ruby-version: ruby
+          bundler-cache: true
+
+      - name: bundle update
+        run: |
+          set -xe
+          bundle config path vendor/bundle
+          bundle update --all --jobs $(nproc) --retry 3
+
+      - name: yard generating test
+        run: |
+          set -xe
+          bundle exec yard
+          ls -ld doc/
+
+      - name: Slack Notification (not success)
+        uses: act10ns/slack@cfcc30955fe9377f4f55e1079e5419ee1014269f # v2
+        if: "! success()"
+        continue-on-error: true
+        with:
+          status: ${{ job.status }}
+          webhook-url: ${{ secrets.SLACK_WEBHOOK }}
+
   all-pass:
     if: always()
 
@@ -112,6 +144,7 @@ jobs:
       - test
       - rubocop
       - rbs
+      - yard
 
     runs-on: ubuntu-latest
 
diff --git a/ruby_header_parser.gemspec b/ruby_header_parser.gemspec
index f17403e..86bae14 100644
--- a/ruby_header_parser.gemspec
+++ b/ruby_header_parser.gemspec
@@ -36,8 +36,10 @@ Gem::Specification.new do |spec|
   # Uncomment to register a new dependency of your gem
   # spec.add_dependency "example-gem", "~> 1.0"
 
+  spec.add_development_dependency "irb"
   spec.add_development_dependency "rake"
   spec.add_development_dependency "rbs", ">= 3.7.0"
+  spec.add_development_dependency "rdoc"
   spec.add_development_dependency "rspec"
   spec.add_development_dependency "rspec-its"
   spec.add_development_dependency "rspec-parameterized"