We'll have some unit tests that depend on locally-placed files (in

particular, .jar files). To keep this manageable, there's now a

tests/deps/ directory that unit tests can use for looking up placed

files, and a get_test_dep_path() method to aid in that.
No tests use this yet, but that will be changing with all Java-backed

tests shortly, to avoid a dependency (and issues with) $CLASSPATH.

Used this in some upcoming unit tests successfully.