diff --git a/.github/workflows/linux.yml b/.github/workflows/linux.yml
index be5dfa4..1abea83 100644
--- a/.github/workflows/linux.yml
+++ b/.github/workflows/linux.yml
@@ -8,7 +8,7 @@ jobs:
     strategy:
       fail-fast: false
       matrix:
-        ruby: [ '2.5', '2.6', '2.7' ]
+        ruby: [ '2.7', '3.0', '3.1', '3.2', '3.3', '3.4' ]
         os:
           - ubuntu-latest
     name: Ruby ${{ matrix.ruby }} unit testing on ${{ matrix.os }}
@@ -17,10 +17,9 @@ jobs:
     - uses: ruby/setup-ruby@v1
       with:
         ruby-version: ${{ matrix.ruby }}
+        bundler-cache: true
     - name: unit testing
       env:
         CI: true
       run: |
-        gem install bundler rake
-        bundle install --jobs 4 --retry 3
         bundle exec rake test
diff --git a/.github/workflows/macos.yml b/.github/workflows/macos.yml
index 4a50081..c3c7afd 100644
--- a/.github/workflows/macos.yml
+++ b/.github/workflows/macos.yml
@@ -8,7 +8,7 @@ jobs:
     strategy:
       fail-fast: false
       matrix:
-        ruby: [ '2.5', '2.6', '2.7' ]
+        ruby: [ '2.7', '3.0', '3.1', '3.2', '3.3', '3.4' ]
         os:
           - macOS-latest
     name: Ruby ${{ matrix.ruby }} unit testing on ${{ matrix.os }}
@@ -17,10 +17,9 @@ jobs:
     - uses: ruby/setup-ruby@v1
       with:
         ruby-version: ${{ matrix.ruby }}
+        bundler-cache: true
     - name: unit testing
       env:
         CI: true
       run: |
-        gem install bundler rake
-        bundle install --jobs 4 --retry 3
         bundle exec rake test
diff --git a/.github/workflows/windows.yml b/.github/workflows/windows.yml
index 41c5582..b3da332 100644
--- a/.github/workflows/windows.yml
+++ b/.github/workflows/windows.yml
@@ -8,7 +8,7 @@ jobs:
     strategy:
       fail-fast: false
       matrix:
-        ruby: [ '2.5', '2.6', '2.7' ]
+        ruby: [ '2.7', '3.0', '3.1', '3.2', '3.3', '3.4' ]
         os:
           - windows-latest
     name: Ruby ${{ matrix.ruby }} unit testing on ${{ matrix.os }}
@@ -17,10 +17,9 @@ jobs:
     - uses: ruby/setup-ruby@v1
       with:
         ruby-version: ${{ matrix.ruby }}
+        bundler-cache: true
     - name: unit testing
       env:
         CI: true
       run: |
-        gem install bundler rake
-        bundle install --jobs 4 --retry 3
         bundle exec rake test
diff --git a/test/plugin/test_out_irc.rb b/test/plugin/test_out_irc.rb
index fa7b854..16fd4c7 100644
--- a/test/plugin/test_out_irc.rb
+++ b/test/plugin/test_out_irc.rb
@@ -19,23 +19,17 @@ def setup
     Fluent::Engine.now = Time.now
   end
 
-  def config(
-    port: PORT,
-    channel: CHANNEL,
-    channel_keys: "",
-    command: COMMAND.to_s,
-    command_keys: nil
-  )
-    config = %[
+  def config(options = {})
+    data = %[
       type irc
       host localhost
-      port #{port}
-      channel #{channel}
-      channel_keys #{channel_keys}
+      port #{options.fetch(:port, PORT)}
+      channel #{options.fetch(:channel, CHANNEL)}
+      channel_keys #{options.fetch(:channel_keys, "")}
       nick #{NICK}
       user #{USER}
       real #{REAL}
-      command #{command}
+      command #{options.fetch(:command, COMMAND.to_s)}
       message #{MESSAGE}
       out_keys tag,time,msg
       time_key time
@@ -44,8 +38,9 @@ def config(
       send_queue_limit 10
       send_interval 0.5
     ]
-    config += %[command_keys #{command_keys}] if command_keys
-    config
+    command_keys = options.fetch(:command_keys, nil)
+    data += %[command_keys #{command_keys}] if command_keys
+    data
   end
 
 
@@ -73,25 +68,25 @@ def test_configure
   end
 
   def test_configure_channel_keys
-    d = create_driver(config(channel:"%s", channel_keys:"channel"))
+    d = create_driver(config({channel:"%s", channel_keys:"channel"}))
     assert_equal "#%s", d.instance.channel
     assert_equal ["channel"], d.instance.channel_keys
   end
 
   def test_configure_command_keys
-    d = create_driver(config(command:"%s", command_keys:"command"))
+    d = create_driver(config({command:"%s", command_keys:"command"}))
     assert_equal "%s", d.instance.command
     assert_equal ["command"], d.instance.command_keys
   end
 
   def test_configure_command
     assert_raise Fluent::ConfigError do
-      create_driver(config(command: 'foo'))
+      create_driver(config({command: 'foo'}))
     end
 
-    assert_nothing_raised { create_driver(config(command: 'priv_msg')) }
-    assert_nothing_raised { create_driver(config(command: 'privmsg')) }
-    assert_nothing_raised { create_driver(config(command: 'notice')) }
+    assert_nothing_raised { create_driver(config({command: 'priv_msg'})) }
+    assert_nothing_raised { create_driver(config({command: 'privmsg'})) }
+    assert_nothing_raised { create_driver(config({command: 'notice'})) }
   end
 
   def test_emit
@@ -111,7 +106,7 @@ def test_emit
       s = IRCParser.parse(socket.gets)
       m[s.class.to_sym] = s
 
-      s = IRCParser.parse(socket.gets)
+      s = IRCParser.parse(socket.gets&.force_encoding("utf-8"))
       m[s.class.to_sym] = s
 
       assert_equal ["##{CHANNEL}"], m[:join].channels