Create Integration tests / ITs for core project

[avelx]

Here is the original thread conversation

We need to create an integration test to make changes in the internal core logic:

• These ITs should be designed in a way we can test core logic in the concurrent environment: so we need a "happy path" along with the scenarios where failures would potentially be expected.

Example of the logic we want to test as a part of these tests: #1264

[yanns]

Those integration tests should stress concurrent resolution, with Future, Fetchers.

[avelx]

Those integration tests should stress concurrent resolution, with Future, Fetchers.

I was thinking of trying the next approach:
https://github.com/sbt/sbt-multi-jvm
https://doc.akka.io/libraries/akka-core/current/multi-jvm-testing.html?language=scala#multi-jvm-testing

I suspect that there is no need to invent a wheel here, and we can use a similar approach.

Multi JVM Testing
Supports running applications (objects with main methods) and ScalaTest tests in multiple JVMs at the same time. Useful for integration testing where multiple systems communicate with each other

[yanns]

Why do you think we'd need multiple JVMs?

[avelx]

Why do you think we'd need multiple JVMs?

I agree, this would be an overkill to use multiple JVM testing here, as I remember this was useful for clustering testing etc;
Let me see if I can do a simple ITs set up first

[avelx]

Here is the overall direction where I am heading with ITs:
https://github.com/sangria-graphql/sangria/pull/1285/changes