Add unit tests for more caching permutations

There are a number of permutations of expired content, invalidated content, evicted content with and without `onlyIfCached` and used in `get` and `search`, with and without a defined source on the table, that we should offer better coverage for.

Start by locating the existing cache unit tests and the implementations of get and search. Map the expired, invalidated, and evicted content cases across onlyIfCached, source presence, and both entry points; done means the listed permutations have focused tests and the suite passes.

Written by the indexing model from the issue text.