  In the past few years, there has been a resurgence in studies towards
space-based optical/infrared interferometry, particularly with the vision to
use the technique to discover and characterise temperate Earth-like exoplanets
around solar analogues. One of the key technological leaps needed to make such
a mission feasible is demonstrating that formation flying precision at the
level needed for interferometry is possible. Here, we present $\textit{Pyxis}$,
a ground-based demonstrator for a future small satellite mission with the aim
to demonstrate the precision metrology needed for space-based interferometry.
We describe the science potential of such a ground-based instrument, and detail
the various subsystems: three six-axis robots, a multi-stage metrology system,
an integrated optics beam combiner and the control systems required for the
necessary precision and stability. We end by looking towards the next stage of
$\textit{Pyxis}$: a collection of small satellites in Earth orbit.
