AsynchronousEventStoreTest#mailentity is flickering

Wanted but not invoked:
observation.notify(
    <any org.xwiki.eventstream.events.MailEntityAddedEvent>,
    event = [null at null by null on null with id id2], entityId = [entity4]
);
-> at org.xwiki.eventstream.internal.AsynchronousEventStoreTest.mailentity(AsynchronousEventStoreTest.java:423)

However, there were exactly 5 interactions with this mock:
observation.notify(
    org.xwiki.eventstream.events.EventStreamAddedEvent@5f59ea8c,
    null at null by null on null with id id1
);
-> at org.xwiki.eventstream.internal.AbstractAsynchronousEventStore.complete(AbstractAsynchronousEventStore.java:466)

observation.notify(
    org.xwiki.eventstream.events.EventStreamAddedEvent@50ab56e2,
    null at null by null on null with id id2
);
-> at org.xwiki.eventstream.internal.AbstractAsynchronousEventStore.complete(AbstractAsynchronousEventStore.java:466)

observation.notify(
    org.xwiki.eventstream.events.MailEntityAddedEvent@7b5b5bfe,
    event = [null at null by null on null with id id1], entityId = [entity1]
);
-> at org.xwiki.eventstream.internal.AbstractAsynchronousEventStore.complete(AbstractAsynchronousEventStore.java:486)

observation.notify(
    org.xwiki.eventstream.events.MailEntityAddedEvent@38ee7a9d,
    event = [null at null by null on null with id id1], entityId = [entity3]
);
-> at org.xwiki.eventstream.internal.AbstractAsynchronousEventStore.complete(AbstractAsynchronousEventStore.java:486)

observation.notify(
    org.xwiki.eventstream.events.MailEntityAddedEvent@629984eb,
    event = [null at null by null on null with id id2], entityId = [entity1]
);
-> at org.xwiki.eventstream.internal.AbstractAsynchronousEventStore.complete(AbstractAsynchronousEventStore.java:486)


	at org.xwiki.eventstream.internal.AsynchronousEventStoreTest.mailentity(AsynchronousEventStoreTest.java:423)
	at java.base/java.lang.reflect.Method.invoke(Method.java:566)
	at java.base/java.util.ArrayList.forEach(ArrayList.java:1540)
	at java.base/java.util.ArrayList.forEach(ArrayList.java:1540)