There's been reasonable investment in PubSub over the last 12 months, but we have no idea if it'll continue to work, even though this is a core feature that many would consider "mission critical".
Unit test coverage is at 4%.
For a XEP with ~200 sections, the Smack test suite contains 2 PubSub tests.
Look for opportunities to increase unit test coverage
Analyse existing coverage of the XEP and contribute additional tests to Smack (or sibling repository)