  We test the cosmological principle by fitting a dipolar modulation of
distance modulus and searching for an evolution of this modulation with respect
to cosmological redshift. Based on a redshift tomographic method, we divide the
Joint Light-curve Analysis compilation of supernovae of type Ia into different
redshift bins, and employ a Markov-Chain Monte-Carlo method to infer the
anisotropic amplitude and direction in each redshift bin. However, we do not
find any significant deviations from the cosmological principle, and the
anisotropic amplitude is stringently constrained to be less than a few
thousandths at $95\%$ confidence level.
