aggregate and publish coverage

.github/workflows/test.yml

@@ -66,3 +66,39 @@ jobs:
           path: coverage/
           include-hidden-files: true
 
+  coverage:
+    needs: test
+    runs-on: ubuntu-latest
+    permissions:
+      pages: write
+      id-token: write
+
+    steps:
+      - uses: actions/checkout@v4
+
+      - name: Setup Ruby
+        uses: ruby/setup-ruby@v1
+        with:
+          ruby-version: 3.4
+          bundler-cache: true
+
+      - name: Download coverage results
+        uses: actions/download-artifact@v4
+        with:
+          pattern: coverage-*
+          path: coverage
+
+      - name: coverage
+        env:
+          CI: 1
+        run: |
+          find coverage -name "*resultset.json" -exec sed -i 's?${{ github.workspace }}?'`pwd`'?' {} \;
+          bundle exec rake coverage:report
+
+      - uses: joshmfrankel/simplecov-check-action@main
+        with:
+          github_token: ${{ secrets.GITHUB_TOKEN }}
+
+      - name: Publish coverage report
+        uses: actions/deploy-pages@v4
+        id: deployment

Rakefile

@@ -13,6 +13,18 @@ require "rubocop/rake_task"
 
 RuboCop::RakeTask.new
 
+namespace :coverage do
+  desc "Aggregates coverage reports"
+  task :report do
+    return unless ENV.key?("CI")
+
+    require "simplecov"
+
+    puts Dir["coverage/**/.resultset.json"].inspect
+    SimpleCov.collate Dir["coverage/**/.resultset.json"]
+  end
+end
+
 if RUBY_ENGINE == "ruby" && RUBY_VERSION > "3.0.0" && !Gem.win_platform?
   task :type_check do
     # Steep doesn't provide Rake integration yet,