Implementation of old EventExeptions

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

@@ -0,0 +1,35 @@
+package mops.gruppen2.domain.event;
+
+import mops.gruppen2.domain.Exceptions.EventException;
+import mops.gruppen2.domain.Exceptions.UserAlreadyExistsException;
+import mops.gruppen2.domain.Group;
+import mops.gruppen2.domain.User;
+import org.junit.jupiter.api.Test;
+
+import static mops.gruppen2.domain.Role.MEMBER;
+import static org.assertj.core.api.Assertions.assertThat;
+import static org.junit.jupiter.api.Assertions.*;
+
+class AddUserEventTest {
+
+    @Test
+    public void userAllreadyExistExeption() throws EventException {
+        Group group = new Group();
+
+        User user = new User("user1","Stein", "Speck", "@sdasd");
+
+        group.getMembers().add(user);
+
+        Event event1 = new AddUserEvent(4L, "user2", "Rock", "Roll", "and");
+        event1.apply(group);
+
+        Event event2 = new AddUserEvent(4L, "user1", "Rock", "Roll", "and");
+
+        assertThrows(UserAlreadyExistsException.class, ()->
+                event2.apply(group)
+                );
+        assertThat(group.getMembers().size()).isEqualTo(2);
+    }
+
+
+}