  Binary pulsars are affected by general relativity (GR), causing the spin axes
of each pulsar to precess. We present polarimetric radio observations of PSR
J1906+0746 that demonstrate the validity of the geometrical model of pulsar
polarisation. We reconstruct the (sky-projected) polarisation emission map over
the pulsar's magnetic pole and predict the disappearance of the detectable
emission by 2028. Two additional tests of GR are performed in this system,
including the spin-precession for strongly self-gravitating bodies. We
constrain the relativistic treatment of the pulsar polarisation model and
measure the pulsar beaming fraction, with implications for the population of
neutron stars and the expected rate of neutron star mergers.
