There are videos on YouTube that show how to make a 1:1 current balun. When the balun is done some people connect a 100W 50 Ohms resistor to the balun and measure SWR say in 7.000-7.200 MHz range. If SWR is low they conclude that the balun works as expected.
Why SWR, i.e. a measure of reflected power, has anything to do with common mode current that the balun suppose to cut off? Or maybe these hams just don't know what they are doing and the test is worthless?
I tried to ask the authors of corresponding videos, but unfortunately they didn't reply.