refactor local file specs to use let blocks
remove mock/stubs of value objects. mv setup to contexts

- Prefer using real objects to mocks for value objects.
- Prefer creating test context via context instead of in the example
remove non-functional conditional fetch from local file

Local file's conditional fetch was based around the previous API where
the remote file provider set the last updated time. This was removed
because of issues with multiple URL/mirroring support.