You can see demo version here

We created some test projects/tasks/tickets etc.
and added several users with different users right:

Administrator (have full access)
Password: administrator

Client (can view only his projects and have access to tickets)
Password: client

Developer (have access to projects and tasks, no configuration/users access)
Password: developer

Note: Attachments don’t work in demo version. Original demo data refresh each hour.

also if you can’t login (might somebody deleted default users) then you can login as root and create user

Password: admin

Note: root user can create users and manage configuration only. You have to create users with user rights to manager projects/tasks etc.