Summary

Add SDAM tests to ensure the TopologyType remains "Single" when a standalone node is restarted as a replica set or mongos.

The SDAM spec says:

The TopologyDescription's type was initialized as Single and remains Single forever. There is always one ServerDescription in TopologyDescription.servers.

PyMongo supports online change from standalone to replica set and standalone to sharded. The tests added in this change would confirm that behavior in all drivers.

Motivation

Who is the affected end user?

Who are the stakeholders?

How does this affect the end user?

Are they blocked? Are they annoyed? Are they confused?

How likely is it that this problem or use case will occur?

Main path? Edge case?

If the problem does occur, what are the consequences and how severe are they?

Minor annoyance at a log message? Performance concern? Outage/unavailability? Failover can't complete?

Is this issue urgent?

Does this ticket have a required timeline? What is it?

Is this ticket required by a downstream team?

Needed by e.g. Atlas, Shell, Compass?

Is this ticket only for tests?

Does this ticket have any functional impact, or is it just test improvements?

Acceptance Criteria

What specific requirements must be met to consider the design phase complete?