The test 'closes MultiSession backend connections' sets createdSess.EXPECT().Close().Return(nil).Times(1) but never seeds MetadataKeyTokenHash into storage, causing Terminate to take the Phase 1 placeholder path instead of the Phase 2 path that calls sm.sessions.Remove() → onEvict → Close(); gomock will fail at teardown with 'expected call to Close() Times(1), called 0 times'. The fix is to capture storage from newTestSessionManager (currently discarded as _) and call storage.Upsert with Metadat

The test helper configurableFailDataStorage overrides Upsert, Create, and Delete — but not Update. This PR changed Terminate's Phase 1 path to call storage.Update instead of storage.Upsert, so the failure-injection counter (shouldFail) is never incremented for Update calls. Both fallback tests — "placeholder termination falls back to delete when upsert fails" and "placeholder termination fails when both upsert and delete fail" — silently pass the Update call through to the real storage, causing 

In the `!found` branch of `ValidatingCache.Get` (pkg/cache/validating_cache.go:135-138), when a concurrent winner is evicted by LRU pressure between `ContainsOrAdd` and `lruCache.Get`, the freshly-loaded value `v` is returned to the caller without calling `onEvict(key, v)`. For the session manager use case, `onEvict` is `sess.Close()` which releases backend HTTP connections — skipping it means those connections are never closed, leaking resources. The fix is to call `c.onEvict(key, v)` in the `!