test: run 'make test' in pipeline

.gitlab-ci.yml

@@ -32,6 +32,12 @@ check_code:
   script:
     liquidsoap --check src/engine.liq
 
+run_tests:
+  stage: test
+  script:
+    - cd tests
+    - liquidsoap engine_test_suite.liq
+
 docker-push:
   # Use the official docker image.
   image: docker:latest