diff --git a/.devcontainer/devcontainer.json b/.devcontainer/devcontainer.json
index 905d5379..7449c31e 100644
--- a/.devcontainer/devcontainer.json
+++ b/.devcontainer/devcontainer.json
@@ -3,7 +3,7 @@
 {
 	"name": "spring",
 	// Or use a Dockerfile or Docker Compose file. More info: https://containers.dev/guide/dockerfile
-	"image": "ghcr.io/rails/devcontainer/images/ruby:3.4.4",
+	"image": "ghcr.io/rails/devcontainer/images/ruby:4.0.0",
 	"features": {
 		"ghcr.io/devcontainers/features/github-cli:1": {}
 	}
diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index 210a42bf..c00289e7 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -6,8 +6,8 @@ jobs:
     strategy:
       fail-fast: false
       matrix:
-        ruby: [ '3.1', '3.2', '3.3', '3.4', 'head' ]
-        rails: [ '7.1', '7.2', '8.0', 'edge' ]
+        ruby: [ '3.1', '3.2', '3.3', '3.4', '4.0', 'head' ]
+        rails: [ '7.1', '7.2', '8.0', '8.1', 'edge' ]
         rubyopt: [""]
         include:
           - ruby: '3.3'
@@ -16,9 +16,12 @@ jobs:
         exclude:
           - ruby: '3.1'
             rails: 'edge'
-            rubyopt: ''
           - ruby: '3.1'
             rails: '8.0'
+          - ruby: '3.1'
+            rails: '8.1'
+          - ruby: '3.2'
+            rails: 'edge'
 
     env:
       RAILS_VERSION: ${{ matrix.rails }}
@@ -41,3 +44,15 @@ jobs:
         run: bundle exec rake test:acceptance RUBYOPT="${{ matrix.rubyopt }}"
         timeout-minutes: 10
         if: ${{ matrix.rails != 'edge' && matrix.ruby != 'head' }} # Acceptance tests use `gem install rails && rails new`
+
+  summary:
+    runs-on: ubuntu-latest
+    needs: tests
+    if: always()
+    steps:
+      - name: Check test matrix results
+        run: |
+          if [ "${{ needs.tests.result }}" != "success" ]; then
+            echo "Tests failed or were cancelled"
+            exit 1
+          fi
diff --git a/Gemfile b/Gemfile
index 59339f17..43bc15d7 100644
--- a/Gemfile
+++ b/Gemfile
@@ -13,3 +13,5 @@ elsif ENV["RAILS_VERSION"]
 else
   gem "activesupport"
 end
+
+gem "minitest", "< 6"
diff --git a/test/support/acceptance_test.rb b/test/support/acceptance_test.rb
index 34876755..d4d7f6ed 100644
--- a/test/support/acceptance_test.rb
+++ b/test/support/acceptance_test.rb
@@ -65,6 +65,7 @@ def refute_output_includes(command, not_expected)
       def assert_speedup(ratio = DEFAULT_SPEEDUP)
         if ENV['CI']
           yield
+          assert true
         else
           app.with_timing do
             yield
@@ -673,7 +674,8 @@ def exec_name
 
         FileUtils.cp_r "#{app.gem_home}/", bundle_path.to_s
 
-        app.run! "bundle install --path .bundle --local"
+        app.run! "bundle config set path '.bundle'"
+        app.run! "bundle install --local"
 
         assert_speedup do
           2.times { assert_success "bundle exec rails runner ''" }
diff --git a/test/support/application_generator.rb b/test/support/application_generator.rb
index 84a3403a..ffa15c38 100644
--- a/test/support/application_generator.rb
+++ b/test/support/application_generator.rb
@@ -53,6 +53,7 @@ def generate_files
         FileUtils.rm_rf(application.path("test/performance"))
 
         append_to_file(application.gemfile, "gem 'spring', '#{Spring::VERSION}'")
+        append_to_file(application.gemfile, "gem 'minitest', '< 6'")
 
         append_to_file(application.path("config/boot.rb"), "raise 'BOOM' if ENV['CRASH_ON_BOOT']")