Are there any definitive tests... ?
Unfortunately, no. There are no definitive tests to test the authenticity of a Rudraksha except the discerning eye of an expert. When looking at the bead carefully, you'll find various deep dug lines separating the various faces of the Rudraksha bead. Ironically, humans have known to use their 'extreme skill' and try to 'carve' lines into the Rudraksha or 'wipe' them off, in order to change the faces or 'Mukhis' of the bead... i.e. 'alter' it according to their demands. It is extremely difficult to tell a genuine and a spurious Rudraksha apart, but the discerning eye of an expert can spot these 'manual interventions' and declare whether or not the Rudraksha has been tampered with.
But even within different Rudrakshas, there are some which are far more powerful than others. The criterion of selecting the right bead is not a simple one. It is a definite " Kriya " which the saints used to do to find out powerful Rudraksha and then they use it for Energizing. Experts must examine each bead and find the right ones. Then each bead must be purified thru' ancient rituals and definite kriya which lasts for around 41 days. After purification, one can wear it on a very auspicious day.