introduce JUnit tag "flaky", to exclude tests from running.

[soloturn]

ExampleTest.testClientCreation fails without real reason, mark it flaky at the moment. permit this tag in engine-tests/build.gadle.kts to separate test runs for normal integration tests, and ones which are not stable on github, for currently unknown reasons. normally of course it would be better to fix these tests - but accepting pull requests is coupled on tests running through. now two commands instead of one run all integration tests:

gradle integrationTest
gradle integrationTestFlaky

please do not lightheartedly mark tests as flaky.

[jdrueckert]

In general, this looks good to me.
I made a few suggestions based on my personal preferences of wording and expression, they are not blocking though.

I split the CI stage using the new gradle task you introduced which works nicely 👍
As you can see the tests are executed by the stage matching their tagging:

org.terasology.engine.integrationenvironment.ExampleTest.testClientConnection() failed in the last CI run. This test is one of the other flaky tests in ExampleTest that I mentioned in the last sync. We probably want to mark at least that one "flaky", too.

[jdrueckert]

The delay manager test fails so rarely that I wouldn't mark that one flaky, but the ExampleTests fail more frequently, so let's mark those flaky. Amusingly the one already marked flaky didn't fail this time 😅

[soloturn]

ok, committed your suggestions and squashed into one. i am understanding correct, we still see the cause of any failed integration test?

[BenjaminAmos]

There shouldn't be any flaky tests, however, those flaking tests have little benefit and the failures have been very disruptive. This is likely the most practical path forward right now.

[jdrueckert]

i am understanding correct, we still see the cause of any failed integration test?

in the sense that test failures are still reported including stack trace etc.? yes
but they shouldn't fail the pipeline anymore.