The fact the test has run out makes no difference to getting it retested & I'm baffled as to why you've bought a new one
I suspect 2012/05 might be it's date of manufacture so it's only just run out, otherwise it's been full but unused for 5+ years if it was the test expiry

Paying £40 odd for a 5 year test will put maybe £100 on to the sale value because without test it's worth very little.