Improve CI: Rails matrix in action file

.github/workflows/ci.yml

@@ -9,14 +9,11 @@ jobs:
   test:
     runs-on: ubuntu-latest
     env:
-      BUNDLE_GEMFILE: ${{ github.workspace }}/.gemfiles/${{ matrix.gemfile }}.gemfile
+      RAILS_VERSION: ${{ matrix.rails }}
     strategy:
       matrix:
-        ruby: ['2.6', '2.7', '3.0', '3.1' ]
-        gemfile:
-          - rails-5.2.x
-          - rails-6.0.x
-          - rails-6.1.x
+        ruby: ['2.7', '3.0', '3.1', '3.2' ]
+        rails: ['~> 5.2', '~> 6.0', '~> 6.1', '~> 7.0']
 
     steps:
       - uses: actions/checkout@v2

Gemfile

@@ -4,3 +4,9 @@ gemspec
 
 gem 'pry'
 gem 'simplecov', require: false, group: :test
+
+install_if -> { ENV.fetch('RAILS_VERSION', nil) } do
+  rails_version = ENV.fetch('RAILS_VERSION', nil)
+  gem 'actionpack', rails_version
+  gem 'activesupport', rails_version
+end