  Pulsars are precision celestial clocks. When being put in a binary, the
ticking conveys the secret of underlying spacetime geometrodynamics. We use
pulsars to test if the gravitational interaction possesses a tiny deviation
from Einstein's General Relativity (GR). In the framework of Standard-Model
Extension (SME), we systematically search for Lorentz-violating operators
cataloged by (a) the minimal couplings of mass dimension 4, (b) the CPT
symmetry of mass dimension 5, and (c) the gravitational weak equivalence
principle (GWEP) of mass dimension 8. No deviation from GR was found yet.
