1st line of defence, use something like ponytail to enforce brevity. Use property testing and behavioural testing on top of unit testing. Enforce readability standards so you will be able to understand the tests.

2nd line, code review.

Do the first pass with an agent, ask it to bounce back vacuous or tautological tests. Ask it to verify that the tests verify what they claim to. Then read them yourself.

3rd line, mutation testing. If the tests don't actually catch broken code, kill the mutants.