  The large-scale structure of the Universe is a rich source of information to
test the consistency of General Relativity on cosmological scales. We briefly
describe how the observed distributions of galaxies is affected by
redshift-space distortions, but also by gravitational lensing and other
relativistic effects. Then, we show how one of this relativistic effects, the
gravitational redshift, can be used to build a model independent test that
directly measures the anisotropic stress, i.e. the difference between the two
gravitational potentials that describe spacetime fluctuations of the geometry.
