CI: add stage for unit tests

.gitlab-ci.yml

@@ -40,3 +40,17 @@ build:
     - docker build --tag ${SERVER_IMAGE_TAG} .
     - docker push ${SERVER_IMAGE_TAG}
 
+# ----------------------------------------------------------------------------------------------------------------------
+# test
+# ----------------------------------------------------------------------------------------------------------------------
+unit_tests:
+  stage: test_and_qa
+  image:
+    name: $SERVER_IMAGE_TAG
+    entrypoint: [""]
+  tags:
+    - docker
+  script:
+    - set -x
+    - echo 'Implement these tests!'
+