CI: added unit tests

.gitlab-ci.yml

+test-job:
+  script:
+    - python3 -m venv .venv             # Create Python virtual environment
+    - source .venv/bin/activate         # Activate Python virtual environment
+    - pip3 install -r requirements.txt  # Install Python dependencies
+    - pip3 install pytest               # Install pytest
+    - pytest test/                      # Run tests