The Planck 2015 results, together with the precise measurement of the expansion history of the Universe from the BOSS baryon acoustic oscillations, confirm the standard LCDM model of cosmology to unprecedented precision. However, it still remains to be tested whether general relativity with a cosmological constant can accurately explain the formation and growth of the large-scale structure of the Universe over an extended redshift range. Such tests can now be performed to new accuracy thanks to the depth and density of galaxies of the Dark Energy Survey (DES) and its external correlations with the CMB. I will present preliminary results of DES galaxy clustering as a function of redshift, and the correlation of DES galaxies with the lensing of the CMB, as reconstructed by Planck and the South Pole Telescope. I will show a constraint on the evolution of the linear growth function obtained from the combination of these data. I will conclude by discussing the further possible tests of gravity from structure formation that will be made possible by DES in the near future, by presenting test studies with current pre-DES data.