In 2016 I found an informative picture showing how Russian bladesmiths tested finished products in 1827 at the famous Zlatoust weapon factory. A short Hungarian post was written about it.
A few days ago I stumbled across a Russian video on blade testing at a factory in Ivanovo (Russian Federation, ~250 km from Moscow). 
A very bad method of testing blade flexibility 
The appropriate test 
During this test the tang is fixed, the blade itself is positioned along a straight line, and the position of the tip is marked by a nail, then the tip is moved 100 mm away from the line (a GOST requirement), after this bending it should return to the original position, when the tip is released. At the factory they perform more severe tests than the one required by the relevant state standard, for example they bend the tip almost to 30⁰.
It was really interesting to see real similarities between the old and contemporary testing methods.
- General description of things that will be shown, then measuring the hardness of a blade (~56-58 HRC) [3:38-5:04], then hitting several times a sturdy table with the flat of the tested blade [5:44], bending the blade [9:39] etc.
- As the Russian engineer has explained in the video: this is a really bad method to test the flexibility. It has only one purpose, namely to impress non-specialists. Nevertheless they performed this test to show us that the their blade can withstand even this kind of abuse, without any deformation.
- GOST 2002 (State standard): Bladed weapons for Cossacks... [7:51]