- use beforeEach to ensure tests do not interfere with each other
Notably, the 'when the ops come in a single linear order' test suite
had state-changing tests that were dependent on the correct order.
Also, the assigment of 'this.firstOpTimestamp' was in a test.
- consolidate populating project and doc ids
The doc reference in this.update was undefined.
- fix doc reference in updates
There were two misuses of 'doc_id' instead of 'doc'.
- Move mocking of MockWebApi.getDocument to the top and use
sinon.resetHistory() or sinon.restore() for controlling the stub.
- Add another test for simple transforming of updates
See 'when another client is sending a concurrent update'.
GitOrigin-RevId: 61ca8a1b0172920ad6ab1b604a9b9259cebddaad
