The DAO "FreshnessTest" in the jenkins test suite does nothing because setup.sh runs before it
The test itself works (CRM_Core_CodeGen_FreshnessTest::testDAOs()), but because in jenkins runs setup.sh gets run near the start of the build, a DAO will appear to be updated even if the git tree doesn't have the updated DAO.
The purpose of the freshness test seems to be to make sure you don't forget to include the DAO in PRs when you make changes to an xml schema to add/change/remove a field in core tables. But it's not doing that currently in jenkins runs because it's always comparing against DAOs after setup.sh/GenCode.php has run.
I'm not sure if there's an easy fix, or maybe the test should be removed and replaced with some developer documentation? It wouldn't even work in a local test suite run if you've run GenCode.php, which you would have had to do to physically try out your schema changes.