Bending of light under gravity. Test is shifting of star positions as measured during a solar eclipse. Modern test is radio wave bending from the Viking transmitter around Mars. Astronomers have observed double images of quasars. This is due to regular intervening galaxy between the quasar and us.
Quasars are very far away galaxies.
Perihelion advance of Mercury. 43 arc sec per century. Gravitational red shift . Gravitational waves traveling at the speed of light. Not yet observed.