Not that I am an expert, but I had my first inspection this year 2 weeks ago. 2 looked Q-, since there was no Brood, one had only very few Drone Brood and in the Cells multiple Eggs, but nothing else. I then thought about combining, but was scared about a DLW.
Nevertheless, I added a Test frame to both Hives. A week later, no QC's, no Brood. So, either there was a Queen or the DLW caused it.
We emptied the Hive out away from the Hive Location and waited. In the evening the bees had still not returned, so I decided to take the blanket they were sitting on and move it back into the Hive (trying to shake as many bees into the Hive), because I had the suspicion that maybe there was a Queen and not a DLW and she was sitting there so nobody wanted to leave her.
Next day I opened the Hive, the Blanket was still full of bees. I put it outside and checked each Frame, no Queen. I then checked the blanket and there she was. I think I could have killed her about 10 times with all I had done, but she was ok so I put her into the Hive. I checked today, she was walking around, but still no Brood.
So.... is a Test Frame working 100%? I would say in my case Yes, a Queen is there, but no brood. The Test Frame told me she was there and if I had combined, because I just assumed that could have caused a problem.
After that I checked the second Hive again, because again no QC's and no Brood and again after a while I found a Queen. Rather small and not marked (she should have been red), so she was not easy to spot. I checked her today and she now good very few eggs, at least a start I hope.
So is a Test Frame a good approach? I would say so, because at least it makes you more careful and makes you think about the situation twice...