Make specs pass for both happy path and sad path.

I attempted to DRY things up as best I could here. There were two issues
that caused the existing suite to fail when testing both happy and sad
paths:

1. Need to unwrap spy in afterEach block so it can be rewrapped in
beforeEach block.
2. The user's preferences were being persisted PRIOR to receiving
it's stubbed state (mocking current). Market summary preferences should
always be persisted AFTER the call to 'sinon.stub'.