Singapore Web3 teams: what QA proof do you trust before shipping a proxy upgrade?

I’m testing an upgradeable Solidity system (proxy pattern) and I’m realizing “tests passing” doesn’t automatically mean the upgrade is safe. The scary part is that upgrade failures can look fine in CI but still break production behavior later: storage layout mismatches, initializer mistakes, role/permission drift, or subtle changes in events and invariants that integrations rely on.

This question is coming up for me during web3 interview prep, because upgradeability is often treated as a real “senior signal” in web3 smart contract roles. I’m trying to avoid sounding like I’m repeating buzzwords — I want to show the kind of evidence that matches what recruiters look for in crypto jobs, and what senior engineers would actually trust before signing off an upgrade.

In my current workflow, I test the basic upgrade flow (deploy v1 → upgrade to v2 → run a few calls), but that feels shallow. I want a QA strategy that proves we didn’t accidentally introduce state corruption, privilege changes, or a breaking change that only shows up after real usage patterns.

For people who’ve shipped upgrades in Web3 projects (especially teams hiring in Singapore): what do you actually test? Do you write state migration tests, invariants across versions, storage layout checks, or event compatibility checks? Also, as a QA candidate, what artifacts do you share in interviews to make upgradeability testing feel credible and not like buzzwords?