  In this paper I investigate the possibility to test Einstein's equations with
observations of cosmological large scale structure. I first show that we have
not tested the equations in observations concerning only the homogeneous and
isotropic Universe. I then show with several examples how we can do better when
considering the fluctuations of both, the energy momentum tensor and the
metric. This is illustrated with galaxy number counts, intensity mapping and
cosmic shear, three examples that are by no means exhaustive.
