The three classical tests of general relativity were:
- the perihelion precession of Mercury's orbit
- the deflection of light by the Sun
- the gravitational redshift of light
However, it was later found that the gravitational redshift of light was not a test of general relativity, per se, but of the Einstein equivalence principle upon which genreal relativity is founded upon. The third test in modern eras is the time delay of light as it undergoes deflection due to the curvature of spacetime. All three tests have produced results that agree with predictions made by general relativity, but general relativity still has not been precision tested at the largest scales in cosmology.
(btw, I'm not up to date with general relativity and all, they might have proposed other tests for general relativity that I'm not up to date with, so look around for that info.)