With workspaces, it becomes really easy to collaborate with your teammates. Everyone in the workspace can access the same tests and work on them (granted they have proper permissions). However, while you are working on any test in the workspace, you would not want another person to be able to open and modify the test at the same time.
To avoid this situation, when a workspace has multiple users, once any user starts working on a test and saves it, the test is locked for everyone else. When a test is locked, a small lock icon is shown beside its name in the test list.
Everyone else will still be able to open the test and view the contents and even start simulations for the test, but they can't modify the test until it is unlocked.
The user who has locked the test has an Unlock button, which they can use to unlock the test. The test will automatically get unlocked if the user has closed the tab or if there was no activity for over 30 minutes. Additionally, any user with an Admin role in the workspace will also have the Unlock button in the test editor.