  The observed acceleration of the universe, explained through dark energy,
could alternatively be explained through a modification of gravity that would
also induce modifications in the evolution of cosmological perturbations. We
use new weak lensing data from the COSMOS survey to test for deviations from
General Relativity. The departure from GR is parametrized in a
model-independent way that consistently parametrizes the two-point cosmic shear
amplitude and growth. Using CMB priors, we perform a likelihood analysis. We
find constraints on the amplitude of the signal that do not indicate a
deviation from General Relativity.
