Unity editor tool
Project Validator
The pass that runs before the build does
Missing scripts, null references, broken shaders and out-of-policy imports all fail at runtime, which means a tester or a store reviewer finds them first.
Overview
The Validator walks scenes and prefabs for the failures that only show up when something runs: missing script components, null serialized fields the code dereferences anyway, materials left on a pipeline that no longer exists.
Findings with one correct answer are marked auto-fix and fixed in a batch. The rest are marked manual and left alone, because a validator that guesses is one nobody trusts.