Is there anyway of testing if the DPF regeneration is still working on a 2015 X250 XFS?

I've just had a new battery fitted and before and after fitting the battery, the mechanic plugged in an Autel scanner and the only fault code that came up was PO52F, a permanent fault with the Glow Plug Module System. He tested all the glow plugs and all were fine so he thinks that fitting a new Glow Plug Module will cure this fault.

There are no warning lights on the car and it drives 100% fine but if the Glow Plug Module isn't working, DPF regenerations won't take place - I haven't noticed a DPF regen for a few weeks. Is there anyway of testing if the DPF regeneration is still working? Even if I take the car on a long run, it may not regen the DPF as it's not as though it happens on every long run. Thanks in advance.