I have created several repositories in GitLab. One of those was for testing purposes and has some commits and branches. I want to delete or remove this repository. How can I do this?

1. Go to the project page
2. Select "Settings"
3. Select the "General" section (you must be in the repository you want to delete it)
4. If you have enough rights, then at the bottom of the page will be a button for "Advanced settings" (i.e. project settings that may result in data loss) or "Remove project" (in newer GitLab versions)
5. Push this button and follow the instructions

This is only available for admins/owner. As a mere project maintainer, you do not see the "Remove project" button.