Lava can be used to do functional tests on real hardware. It can be easily installed on PureOS, an FSDG compliant GNU/Linux distribution.
The OsmoGSMTester project is able to be interfaced with the Android RIL through ofono and can emulate a GSM network with the help of a compatible GSM base station or SDR.
The Simtrace 2 project can be used, along with SIM card readers to programmatically feed a SIM card to a smartphone. This can be used to run test on real networks.
The Galaxy S2 (I9100) has an antenna connector