Serve an application built by the pipeline In the company that I work, the frontend application is very complex, so one of our layers of testing includes building/serving the application and testing with integrations mocked (The application isn't deployed anywhere on this step).

Right now we are trying to migrate from Jenkins to Gitlab CI, but I have no clue how to do this. I have the build artifact (Some html/css/js) but I couln't find any information how to share the artifact with some Gitlab CI service.

Basically what I want do achieve is Build -> Serve the application that was built -> Run some tests on it 

Is it possible to do this?
Gitlab CI/CD offers Docker Engine. If you can create a docker image, you can serve the application the same way as you were doing with Jenkins. You can find more details on how to integrate both here. 

Hope it helps.