Add test coverage for blackhole connector

[vlad-lyutenko]

During work on this PR #18016, noticed that test coverage is pretty small.
I think we could refactor current Smoke test to be more consistent with BaseConnectorSmokeTest.
And think about BaseConnectorTest

[SakshamGairola]

Hi @vlad-lyutenko I would like to contribute to this project. Can you assign this ticket me?

[vlad-lyutenko]

Thanks for working on this, please notice we are going to remove materialized view support for this connector (#18628), but anyway it's good idea to add bigger test coverage!

[tsafacjo]

still on going ?
Can I work on it too ?

[vlad-lyutenko]

Can I work on it too ?

Sure, thanks!

[ritishalaungani]

Hi @vlad-lyutenko, I have been taking a look at this ticket, and had a few questions I hope you can answer-

1. Is the goal of this ticket to get BlackHoleConnectorSmoke test to extend from BaseConnectorSmokeTest?
2. If yes, then based on my investigation, this doesn't seem possible. Most of the BaseConnectorSmokeTest methods run various queries on the datasource that assume that the datasource is actually retaining data, which is not the case for the BlackHoleConnector. The assertions would fail because the SELECT queries all return NULL values. Am I thinking about this correctly?
3. Looking through the existing tests in TestBlackHoleSmoke, the coverage seems reasonable to me. Were there any specific queries you found missing and thought should be added to it?

[vlad-lyutenko]

Hi @ritishalaungani,
big thx for your interest to this task.
Maybe some description - I was working on some task connected to Materialised Views and I added some support for MV to blackhole connector, but then I realised, that we need test coverage for MV in blackhole connector.
So that's why this task appeared.
But then later we decided to remove support for MV views in this connector, but task left as it is.
So I think if you think it's enough, we can close it.

But maybe @Praveen2112 have some ideas, how to improve this test coverage.