Take the staking contract you built: draw the state machine, list every external call, name the invariants, and write tests that try to violate each one. Then check the operational side — who holds the keys, how rewards are funded, what happens if the oracle stops, and how users exit if the team disappears.
invariant: address(this).balance >= totalStaked invariant: sum(positions[i].amount) == totalStaked
A protocol is finished when its failure modes are documented, not when it compiles.