Update .gitlab-ci.yml

.gitlab-ci.yml

-image: alpine:latest
+image: node:14.15.4
+cache:
+  untracked: true
+  key: "$CI_BUILD_REF_NAME"
+  paths:
+    - node_modules/
 
-pages:
-  stage: deploy
+stages:
+      - install
+      - unit-testing
+      - deploy-pages
+
+install:
+  stage: install
+  script:
+    - npm install
+    - npm install --only=dev
+
+unit_testing:
+  stage: unit-testing
+  script:
+    - npm run test
+
+deploy_pages:
+  image: alpine:latest
+  stage: deploy-pages
   script:
-  - echo 'Nothing to do...'
+  - echo 'Deploying...'
   artifacts:
     paths:
     - public
-    expire_in: 1 day
   only:
   - master