diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index 0b186e1..0070ff6 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -7,7 +7,7 @@ jobs:
     runs-on: ubuntu-latest
     strategy:
       matrix:
-        ruby: ["2.6", "2.7", "3.0"]
+        ruby: ["3.2", "3.3", "3.4"]
     steps:
       - name: Checkout
         uses: actions/checkout@v2
@@ -20,4 +20,3 @@ jobs:
         env:
           CI: true
         run: bundle exec rake test
-
diff --git a/ep_postmaster.gemspec b/ep_postmaster.gemspec
index fe3e5c8..fb4e7e0 100644
--- a/ep_postmaster.gemspec
+++ b/ep_postmaster.gemspec
@@ -16,7 +16,7 @@ Gem::Specification.new do |s|
   s.files = Dir["{app,config,db,lib}/**/*", "MIT-LICENSE", "Rakefile", "README.rdoc"]
   s.test_files = Dir["test/**/*"]
 
-  s.add_dependency "rails", ">= 4.2.1", "< 8"
+  s.add_dependency "rails", ">= 4.2.1", "< 8.1"
 
   s.add_development_dependency "sqlite3"
   s.add_development_dependency "rr"
@@ -25,4 +25,8 @@ Gem::Specification.new do |s|
   s.add_development_dependency "minitest", "~> 5.1"
   s.add_development_dependency "minitest-reporters-turn_reporter"
   s.add_development_dependency "letter_opener"
+  s.add_development_dependency "base64"
+  s.add_development_dependency "bigdecimal"
+  s.add_development_dependency "mutex_m"
+  s.add_development_dependency "drb"
 end
diff --git a/test/dummy/config/environments/test.rb b/test/dummy/config/environments/test.rb
index f8b102b..1f6501b 100644
--- a/test/dummy/config/environments/test.rb
+++ b/test/dummy/config/environments/test.rb
@@ -36,4 +36,7 @@
 
   # Raises error for missing translations
   # config.action_view.raise_on_missing_translations = true
+
+  # Don't render exception templates for rescuable exceptions; raise for all exceptions.
+  config.action_dispatch.show_exceptions = :none
 end
diff --git a/test/test_helper.rb b/test/test_helper.rb
index d88d915..de1b5f9 100644
--- a/test/test_helper.rb
+++ b/test/test_helper.rb
@@ -10,9 +10,9 @@
 require "minitest/reporters/turn_reporter"
 
 if ENV["CI"] == "true"
-  MiniTest::Reporters.use! [ Minitest::Reporters::TurnReporter.new, MiniTest::Reporters::JUnitReporter.new ]
+  Minitest::Reporters.use! [ Minitest::Reporters::TurnReporter.new, Minitest::Reporters::JUnitReporter.new ]
 else
-  MiniTest::Reporters.use! Minitest::Reporters::TurnReporter.new
+  Minitest::Reporters.use! Minitest::Reporters::TurnReporter.new
 end
 
 Rails.backtrace_cleaner.remove_silencers!