To test the DR you can use a DX-1 102-Db 18 Step Grayscale chart from DSC Labs: HERE , read about a test on the Arri HERE
I do not know how DxO does there testing for raw Dynamic range.
This will give you an engineering spec.
But I don't care if I can see detail in a shadow if there are nasty blobs of color, poor tonal transitions, and choppy luminance noise.
The engineering spec for DR does not care what the shadows look like aesthetically, nor does it take into account the positive effects of pairing hardware/software fine tuned together to produce pleasing end results.
According to DxO an IQ160 had the same DR when I was using it with Capture One v6 as when I was using it with Capture One v7. Technically they are right, but the more pertinent question of "how much could I pull out of shadows from an IQ160 file and still get good results" did change between the two software versions.
To evaluate the "photographically useful DR" of a system I suggest going and taking real world pictures with it, opening it in your preferred software, and seeing how much you can play with the file before it breaks apart
[Real World] > [Lab Tests] any day.