SHITL stands for Some Hardware In The Loop. SHITL testing is a method of testing things before launch, similarly other forms of testing are Hardware in the Loop (HITL) or Hardware Out Of the Loop (HOOTL). The best test is a HITL, which tests all hardware and software components, while a HOOTL is mostly just for software and is a simulation, and a SHITL is somewhere in the middle. It's like shitty version of HITL.
For Valbal, we use a Raspberry Pi to both flash new code to the valbal board, and run tests, all from the comfort of our beds.