diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index b06344e..be384bf 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -22,17 +22,22 @@ jobs:
     strategy:
       fail-fast: false
       matrix:
-        os: [ubuntu-20.04]
-        ruby: ['3.0', '3.1']
+        os: [ubuntu-24.04]
+        ruby:
+          - '3.0'
+          - '3.1'
+          - '3.2'
+          - '3.3'
+          - '3.4'
         include:
-          - { os: ubuntu-20.04 , ruby: ruby-head }
-          - { os: ubuntu-20.04 , ruby: jruby, allow-failure: true }
-          - { os: ubuntu-20.04 , ruby: jruby-head }
-          - { os: ubuntu-20.04 , ruby: truffleruby }
-          - { os: ubuntu-20.04 , ruby: truffleruby-head, allow-failure: true }
+          - { os: ubuntu-24.04 , ruby: ruby-head }
+          - { os: ubuntu-24.04 , ruby: jruby, allow-failure: true }
+          - { os: ubuntu-24.04 , ruby: jruby-head }
+          - { os: ubuntu-24.04 , ruby: truffleruby }
+          - { os: ubuntu-24.04 , ruby: truffleruby-head, allow-failure: true }
     runs-on: ${{ matrix.os }}
     steps:
-    - uses: actions/checkout@v3
+    - uses: actions/checkout@v4
     - uses: ruby/setup-ruby@v1
       continue-on-error: ${{ matrix.allow-failure || false }}
       id: bundle
diff --git a/test/rubygems/mock_gem_ui.rb b/test/rubygems/mock_gem_ui.rb
new file mode 100644
index 0000000..218d4b6
--- /dev/null
+++ b/test/rubygems/mock_gem_ui.rb
@@ -0,0 +1,86 @@
+# frozen_string_literal: true
+
+require "rubygems/user_interaction"
+
+##
+# This Gem::StreamUI subclass records input and output to StringIO for
+# retrieval during tests.
+
+class Gem::MockGemUi < Gem::StreamUI
+  ##
+  # Raised when you haven't provided enough input to your MockGemUi
+
+  class InputEOFError < RuntimeError
+    def initialize(question)
+      super "Out of input for MockGemUi on #{question.inspect}"
+    end
+  end
+
+  class TermError < SystemExit
+    attr_reader :exit_code
+
+    def initialize(exit_code)
+      super
+      @exit_code = exit_code
+    end
+  end
+
+  class SystemExitException < RuntimeError; end
+
+  module TTY
+    attr_accessor :tty
+
+    def tty?
+      @tty = true unless defined?(@tty)
+      @tty
+    end
+
+    def noecho
+      yield self
+    end
+  end
+
+  def initialize(input = "")
+    require "stringio"
+    ins = StringIO.new input
+    outs = StringIO.new
+    errs = StringIO.new
+
+    ins.extend TTY
+    outs.extend TTY
+    errs.extend TTY
+
+    super ins, outs, errs, true
+
+    @terminated = false
+  end
+
+  def ask(question)
+    raise InputEOFError, question if @ins.eof?
+
+    super
+  end
+
+  def input
+    @ins.string
+  end
+
+  def output
+    @outs.string
+  end
+
+  def error
+    @errs.string
+  end
+
+  def terminated?
+    @terminated
+  end
+
+  def terminate_interaction(status=0)
+    @terminated = true
+
+    raise TermError, status if status != 0
+    raise SystemExitException
+  end
+end
diff --git a/test/rubygems/test_gem_commands_compare_command.rb b/test/rubygems/test_gem_commands_compare_command.rb
index b9b099b..04782dd 100644
--- a/test/rubygems/test_gem_commands_compare_command.rb
+++ b/test/rubygems/test_gem_commands_compare_command.rb
@@ -1,6 +1,6 @@
 require_relative '../test_helper'
+require_relative 'mock_gem_ui'
 require 'rubygems/user_interaction'
-require 'rubygems/mock_gem_ui'
 require 'rubygems/commands/compare_command'
 
 class TestGemCommandsCompareCommand < Minitest::Test