When adding some tests for $unionWith, it became clear the framework is all built around the one collection with the unique name. In order to better integrate testing things like $unionwith into the framework, we should be able to opt-in to having the test operate on multiple namespaces. This would allow:
- benefitting from the test setup, including things like sharding the collection.
- Plug in better to simultaneous variants - letting the test infrastructure know about all the collections involved
- Make things easier to manage for the infrastructure and test authors. For example, this code should probably know of all used collections.