feat: Add test backend pipeline

.gitea/workflows/ci.yml

@@ -29,6 +29,32 @@ jobs:
             workflow:
               - '.gitea/workflows/**'
 
+  test-backend:
+    runs-on: ubuntu-latest
+    name: "Backend Tests"
+    needs: changed_files
+    if: ${{ needs.changed_files.outputs.backend == 'true' || needs.changed_files.outputs.workflow == 'true' }}
+    container:
+      image: "cimg/openjdk:23.0-node"
+    steps:
+      - name: "Checkout"
+        uses: actions/checkout@v4
+
+      - name: "Run tests"
+        working-directory: ./backend
+        run: |
+          ./gradlew test
+
+      - name: "Cache checkstyle results"
+        uses: actions/upload-artifact@v4
+        with:
+          name: checkstyle-results
+          path: backend/build/reports/checkstyle
+
+      - name: "Stop Gradle"
+        working-directory: ./backend
+        run: ./gradlew --stop
+
   checkstyle:
     runs-on: ubuntu-latest
     name: "Checkstyle Main"