One teacher wrote: "I was lucky to hear a lecture by Paul Nation and he said we all have a different vocab. It's very hard/impossible to test over 6-9000 words cos we all specialize. Law majors should know legal words, another should know about culture, IT in digital stuff etc. So how do you test that fairly?"
But let's take a step back and ask ourselves an interesting question, Why test it?
All of my students who are professionals (managers, department heads, engineers) have no problem with the vocabulary of their profession yet they don't seem to have actually "studied" it. Their professional vocabulary is actually stronger than their general vocabulary. This is most noticeable in the IT field but happens in all professions. Logistics people know all about "bill of lading", "supply chain management" and "port of entry". Accountants know all about "accounts receivable" and "double entry ledgers".
In the extreme I call this McEnglish. If you go to a McDonald's in any country they can usually take your order in English without too much trouble. However, if you ask them if they think it is going to rain today they are totally lost.
So I'm wondering how necessary it is to worry about teaching professional vocabulary. People will learn it naturally in an Extensive Reading or Comprehensible Input sort of way in their work. If they are already working then they seem to already know it.
However, they are often weak in the grammar around that vocabulary. "It come to a new port of entry" type of thing or "Supply chain management is a big important to our company."