We present Lux, an open source system level test tool with expect like properties. Lux is usable for testing real world scenarios with multiple concurrent sessions. A typical scenario is a server and multiple clients, with synchronisation between sessions (interaction with server and/or clients). Lux is written (almost) entirely in Erlang, with no use of additional libraries, proving Erlang to be a very good fit for this problem. Written in Erlang, Lux is not limited to the testing of systems written in Erlang, but can test any system with text based interfaces or where writing text based adapters is feasible.