Add a unit test

.gitea/workflows/demo.yaml

@@ -4,7 +4,23 @@ run-name: ${{ gitea.actor }} is testing out Gitea Actions 🚀
 on: [push]
 
 jobs:
+  test:
+    runs-on: ubuntu-latest
+    steps:
+      - name: Checkout
+        uses: actions/checkout@v4
+
+      - name: Test
+        uses: ruby/setup-ruby@v1
+        with:
+          ruby-version: '3.3'
+          bundler-cache: true
+
+      - run: ruby app_test.rb
+
+
   release-image:
+    needs: test
     runs-on: ubuntu-latest
     container:
       image: catthehacker/ubuntu:act-latest