.Net NEVM: Specification test suite for providers

[roji]

The current integration tests for NEVM providers are implemented separately for each provider, with no support from the abstraction. To promote better universal coverage and reduce the per-provider work needed, we could expoes a "specification test suite" with the abstraction, which providers implement, and which execute a set of standardized tests to ensure the provider works correctly. A good model here would be the Entity Framework Core specification test suite, which exercises an EF provider in a myriad of ways.

/cc @westey-m

[dmytrostruk]

Small note: I already refactored the integration tests for IVectorStore interface to have a single set of tests for each provider:
https://github.com/microsoft/semantic-kernel/blob/main/dotnet/src/IntegrationTests/Connectors/Memory/BaseVectorStoreTests.cs

I tried to do the same with IVectorStoreRecordCollection interface and it appeared that it's more complicated than IVectorStore, since each provider has some limitations (e.g. the requirements for collection/table/field names, supported index kinds, dimensions etc), which makes it harder to unify into a single test suite to cover all methods in that abstraction and all available connectors. At the end, I noticed that I still need to override some test cases for specific connectors to ensure high coverage and this put the idea of a single test suite under the question.

As an alternative solution, we can keep current tests for specific providers to ensure high coverage but add separate set of test cases (maybe basic ones) using abstraction only and enable it for as many connectors as we can.

[roji]

@dmytrostruk thanks for the context, yeah, that all makes sense. I plan to take a look at this, will share what i come up with. I agree that it's OK if an implementation needs to have its own tests in addition to the "standard" ones it can get for free - I do hope we'll be able to provide a meaningful set of standard ones, without being prevented from testing too much by differences between the database etc.