A simple way to test for edge retention is by paper or cardboard cutting. Using a stack of paper, see how many times it can be sliced through before the blade gets noticeably dull. This is a little subjective but still a usable measurement.
The brass rod test, this is simply pressing the edge of the blade on angle against a brass rod and watching to see the edge flex and return to position after the pressure is released. Be aware that not all metals will flex, some higher alloy steels will chip rather than flex in this test, even when performed correctly
Every so often, and every time a major change is made to the blade making process, a blade will need to be taken to its ultimate end. This is the death of every blade tested, why? It is the only way to know what it will take to fail. It is better to find out in the shop what a blade can do, and what makes it fail, than after its in the hand of an end user. Obviously these tests are not done very often, they are selectively done, based on what is needed to be discovered.
Chopping nails with a knife shows edge retention under abusive conditions. Use a mallet to drive the blade into the nail. A normal knife is not expected to be used this way, but hitting bone while cleaning game can be almost as destructive to the cutting edge. This is a test of that issue to the extreme.
Bending Giving the blade a 90 degree bend or some rotational twisting shows how the heat treat leaves the blade flexible while still having a good cutting edge. Once again under normal use this would never happen, but accidents can occur and people do abuse blades quite often. This shows how well a blade responds. Remember to cover the blade with a section of pipe or an old welding glove to contain any flying pieces when it breaks. Examine the pieces, look at how it broke and the grain exposed on the edges. That will reveal much about the heat treat.