Previously we wouldn't send deletions for this, even though they shift
all elements to the left. Add a battery of unit tests for the list delta
algorithm, and standardise on the practice of issuing a DELETE prior to
an INSERT for newly inserted rooms, regardless of where in the window
they appear. Previously, we may skip the DELETE at the end of the list,
which was just inconsistent of us.
In preparation for migrating end-to-end style integration tests
to be actual end-to-end tests. The intended split is:
- Does the test exclusively use the public sliding sync API for test assertions?
- Does the test exclusively use the public sync v2 API for configuring the test?
If the answer to both questions is YES, then they should be end-to-end tests.
Some examples of this include testing core functionality of the API like
room subscriptions, multiple lists, filters, extensions, etc.
Some examples of tests which are NOT end-to-end tests include:
- Testing connection handling (e.g sending multiple duplicate requests)
- Ensuring outstanding requests get cancelled.
- Testing restarts of the proxy.
- Testing out-of-order responses.
- Benchmarks.
These all involve configuring the test / asserting different things, which would
be extremely difficult to reliably engineer using a real homeserver.
