The most common and most likely answer to this crossword clue is the 9 letter word AUDITIONS
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More clues leading to the result AUDITIONS
Buddy explains!

The straight part
We know that "tests" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case tests = auditions.The cryptic/wordplay part
In cryptic crossword there's often an wordplay/cryptic part as well.This part involves a more complex hint, such as an anagram, homophone, hidden word, etc.
Sadly, We don't have an explanation for this specific crossword clue yet.
What does AUDITIONS mean?
AUDITIONS noun- A performance, by an aspiring performer, to demonstrate suitability or talent.
- The sense of hearing.
- An act of hearing; being heard.
- Something heard.
- To evaluate one or more performers in through an audition.
- To take part in such a performance.