Is this expected behaviour for SMTRunnerEventsListener? Follow

I have my own

SMTRunnerEventsListener

and I am overriding the onTestFinished() method. What I observed is that if I block the onTestFinished() method (I do not return for a while), then the next unit test is not started. This is expected behavior and I need this functionality for my plugin. But I have observed that this does not work for the second test for some reason(when I run a test class which contains many methods annotated with @Test). I am using JUnit 5.

So if I have 

@Override
public void onTestFinished(@NotNull SMTestProxy smTestProxy) {
    try {
        Thread.sleep(9000);
    } catch (InterruptedException e) {
        e.printStackTrace();
    }
}

The second test is started even before the sleep is over(third unit test is not started). Is this a bug or expected behavior?