new individual event-tests + removed old comments + removed doubled exception

Co-authored-by: Christoph <tobi@urpost.de>

src/test/java/mops/gruppen2/domain/event/EventTest.java

@@ -0,0 +1,24 @@
+package mops.gruppen2.domain.event;
+
+import mops.gruppen2.TestBuilder;
+import mops.gruppen2.domain.Group;
+import mops.gruppen2.domain.exception.GroupIdMismatchException;
+import org.junit.jupiter.api.Test;
+
+import static mops.gruppen2.TestBuilder.createPublicGroupEvent;
+import static mops.gruppen2.TestBuilder.uuidFromInt;
+import static org.junit.jupiter.api.Assertions.assertThrows;
+
+class EventTest {
+
+    @Test
+    void apply() {
+        Event createEvent = createPublicGroupEvent(uuidFromInt(0));
+        Event addEvent = TestBuilder.addUserEvent(uuidFromInt(1));
+
+        Group group = TestBuilder.apply(createEvent);
+
+        assertThrows(GroupIdMismatchException.class, () -> addEvent.apply(group));
+    }
+
+}