As Mr. Ezazi mentioned Tension test is the most preferred one to measure the ductility in a material, but there could be many other estimations and correlations that can be made on the ductility based on the hardness and torsion tests too... And the answer to the other question of yours on the effect of yield strength on the ductility is that the ductility of a material sees a significant decrease if the yield strength is increased, but at the same time I remember reading a recent study wherein they found that the ductility and strength were simultaneously found to be high due to the nanostructures of the materials that were subjected to severe plastic deformation processing. But in general they are inversely proportional to each other...
I agree with both Amin and Akshay. Just to note that the values for % elongation or % reduction in area will not necessarily be the equal for the same material.