I tried my first fixer test yesterday as well and went through the same phase of not quite knowing what to expect. I used some scraps from APX 100 for the tests. My problem was not understanding exactly what clearing means. In the end it means exactly that - the removal of the grey emulsion leaving a clear, see-through strip of plastic.
The problem was that APX base has quite a dark purple tint to it, compared to HP5, which I'm used to using. HP5 is pretty much clear & uncoloured. So when I dropped the APX clip into the fixer, it cleared very quickly. But because of the dark tint to the plastic it looked like it changed from grey to black which was the opposite to what I expected! It really confused me for a while, and I repeated it with fresh, undiluted fixer and was beginning to think the whole bottle had gone off overnight.
Eventually when I held the clips up to the light I realise that the emulsion had indeed cleared away and all I had left was the transparent plastic. I felt like a real fool.
So anyway, try repeating what you did. Put a drop on a clip of film (make sure it's on the grey emulsion side) and after a minute try giving the clip a quick rinse in water to wash the fixer off. Hold it up to the light and you should see a transparent circle surrounded by the grey of the emulsion. When you drop it into the fixer, once you can no longer see the circle, all the emulsion has cleared. Double this time is the recommended fixing time.
