I am not sure, but flight testing equipment i know about are extended probes and sensors. But the pod in the picture in airforces monthly is a closed and very large rectangular pod. Not saying its not flight testing equipment, but its a strange and very large shaped pod if it is.
If you google Ka-50/52 images, you'll find hundreds of photos with the same pod. I'm not sure exactly what is contains, but I would guess more recording equipment than measuring sensors. The case itself may just be a universal container. Maybe they even use it as a travel pod.
I was wondering if its more of a submerine or aquatic radar sensor for anti sub use as it was loaded on a 52 on the back of a ship?
I doubt it, but there is a naval Ka-52K model in development (haven't read the article, but suspect it talked about it). Besides the airframe modifications (folding wings and rotors), this may have some additional sensors and armament.