Mix cassettes -- people refer back to them (4,5)

I believe the answer is:

test cases

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'people refer back to them' is the definition.
I can't judge whether this defines the answer.

'mix cassettes' is the wordplay.
'mix' indicates an anagram.
'cassettes' with letters rearranged gives 'TEST CASES'.

Can you help me to learn more?

(Other definitions for test cases that I've seen before include "They set a precedent" , "Precedents" .)

I've seen this clue in The Telegraph.

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