add Test for checkGroup Method

src/test/java/mops/gruppen2/service/EventServiceTest.java

@@ -1,7 +1,40 @@
 package mops.gruppen2.service;
 
+import mops.gruppen2.domain.EventDTO;
+import mops.gruppen2.domain.event.Event;
+import mops.gruppen2.repository.EventRepository;
+import org.junit.jupiter.api.BeforeAll;
+import org.junit.jupiter.api.BeforeEach;
+import org.junit.jupiter.api.Test;
+
+import java.util.ArrayList;
+import java.util.List;
+
 import static org.junit.jupiter.api.Assertions.*;
+import static org.mockito.Mockito.mock;
+import static org.mockito.Mockito.when;
 
 class EventServiceTest {
+    EventService eventService;
+    EventRepository eventRepositoryMock = mock(EventRepository.class);
 
+    @BeforeEach
+    void setUp(){
+        eventService = new EventService(mock(SerializationService.class),eventRepositoryMock);
+    }
+
+    @Test
+    void checkGroupTest(){
+        EventDTO eventDTO = new EventDTO();
+        EventDTO eventDTO1 = new EventDTO();
+        eventDTO1.setGroup_id(1L);
+        eventDTO.setUser_id("realer");
+        eventDTO.setUser_id("faker");
+        eventDTO.setGroup_id(0L);
+        List<EventDTO> eventDTOS = new ArrayList<>();
+        eventDTOS.add(eventDTO);
+        eventDTOS.add(eventDTO1);
+        when(eventRepositoryMock.findAll()).thenReturn(eventDTOS);
+        assertEquals(eventDTO1.getGroup_id()+1, eventService.checkGroup());
+    }
 }