Run tests with xvfb

Author: sandbergja

.github/workflows/ruby.yml

@@ -31,4 +31,4 @@ jobs:
         ruby-version: ${{ matrix.ruby-version }}
         bundler-cache: true # runs 'bundle install' and caches installed gems automatically
     - name: Run tests
-      run: bundle exec rake
+      run: xvfb-run bundle exec rake