Integration Test: hydrateVars

The current hydrateVars specs mock most of the module's external dependencies, which is good for specifying behavior and ensuring modularity, but isn't helping when it comes to refactoring code that touches it.

Start by locating the existing hydrateVars specs and reviewing which external dependencies they mock. Define the integration-test boundary from those specs, then verify the resulting tests exercise the real dependencies while preserving the behavior they currently specify.

Written by the indexing model from the issue text.