Gitlab is a great issue tracker. You can log your project activities like issue status, deadline etc in a git repository. Before that, you need to login to Gitlab and then go to the project where you need to create/manage issues .
Befor launching an application we should test the app to ensure that the application is working as per your requirement or not and to deliver defect free product on time, within the budget. If there is no testing, then there is no quality product.