ci: launch pytest in ci

.gitlab-ci.yml

-build-job:
-  stage: build
-  script:
-    - echo "Hello, $GITLAB_USER_LOGIN!"
+default:
+  image: qnib/pytest:latest
 
-test-job1:
+test:
   stage: test
   script:
-    - echo "This job tests something"
+    - pytest
 
-test-job2:
-  stage: test
-  script:
-    - echo "This job tests something, but takes more time than test-job1."
-    - echo "After the echo commands complete, it runs the sleep command for 20 seconds"
-    - echo "which simulates a test that runs 20 seconds longer than test-job1"
-    - sleep 20