feat: CARITAS-286

* add unit tests for new class TopicEnrichmentService

src/main/java/de/caritas/cob/agencyservice/api/service/TopicEnrichmentService.java

@@ -2,6 +2,7 @@
 
 import de.caritas.cob.agencyservice.api.model.AgencyTopicsDTO;
 import de.caritas.cob.agencyservice.topicservice.generated.web.model.TopicDTO;
+import java.util.ArrayList;
 import java.util.List;
 import java.util.Map;
 import java.util.Objects;
@@ -24,11 +25,23 @@ public List<AgencyTopicsDTO> enrichTopicIdsWithTopicData(List<Integer> topicIds)
     log.debug("Enriching topic ids with topics short titles");
     var availableTopics = topicService.getAllTopics();
     log.debug("Enriching topic ids list with size: {} ", topicIds.size());
-    log.debug("Available topics list has size: {} ", availableTopics.size());
+    logAvailableTopicsList(availableTopics);
     return enrichTopicIds(availableTopics, topicIds);
   }
 
+  private static void logAvailableTopicsList(List<TopicDTO> availableTopics) {
+    if (availableTopics == null) {
+      log.debug("Available topics list is null ");
+    } else {
+      log.debug("Available topics list has size: {} ", availableTopics.size());
+    }
+  }
+
   private List<AgencyTopicsDTO> enrichTopicIds(List<TopicDTO> availableTopics, List<Integer> topicIds) {
+
+    if (availableTopics == null) {
+      return new ArrayList<>();
+    }
     // Create a map of availableTopics to quickly access TopicDTO by id
     Map<Long, String> topicMap = availableTopics.stream()
         .collect(Collectors.toMap(TopicDTO::getId, TopicDTO::getName));

src/test/java/de/caritas/cob/agencyservice/api/service/TopicEnrichmentServiceTest.java

@@ -0,0 +1,87 @@
+package de.caritas.cob.agencyservice.api.service;
+
+import static com.google.common.collect.Lists.newArrayList;
+import static org.assertj.core.api.Assertions.assertThat;
+import static org.mockito.Mockito.when;
+
+import de.caritas.cob.agencyservice.api.model.AgencyTopicsDTO;
+import java.util.List;
+import org.junit.jupiter.api.Test;
+import org.junit.jupiter.api.extension.ExtendWith;
+import org.mockito.InjectMocks;
+import org.mockito.Mock;
+import org.mockito.junit.jupiter.MockitoExtension;
+import de.caritas.cob.agencyservice.topicservice.generated.web.model.TopicDTO;
+
+@ExtendWith(MockitoExtension.class)
+class TopicEnrichmentServiceTest {
+
+  @InjectMocks
+  TopicEnrichmentService topicEnrichmentService;
+
+  @Mock
+  TopicService topicService;
+
+  @Test
+  void enrichTopicIdsWithTopicData_Should_EnrichAgencyWithTopicDataFromTopicService() {
+    // given
+    when(topicService.getAllTopics()).thenReturn(
+        newArrayList(new TopicDTO().id(1L).name("first topic").description("desc"),
+            new TopicDTO().id(2L).name("second topic").description("desc")));
+    List<Integer> topicIds = newArrayList(1, 2);
+
+    // when
+    var result = topicEnrichmentService.enrichTopicIdsWithTopicData(topicIds);
+
+    // then
+    assertThat(result).isNotEmpty();
+    assertThat(result)
+        .extracting(AgencyTopicsDTO::getName)
+        .contains("first topic", "second topic");
+  }
+
+
+  @Test
+  void enrichTopicIdsWithTopicData_Should_ReturnEmptyListIfNoTopicsAreDefined() {
+    // given
+    when(topicService.getAllTopics()).thenReturn(
+        newArrayList());
+    List<Integer> topicIds = newArrayList(1, 2);
+
+    // when
+    var result = topicEnrichmentService.enrichTopicIdsWithTopicData(topicIds);
+
+    // then
+    assertThat(result).isEmpty();
+  }
+
+
+  @Test
+  void enrichTopicIdsWithTopicData_Should_ReturnEmptyListIfTopicsListIsNull() {
+    // given
+    when(topicService.getAllTopics()).thenReturn(
+        null);
+    List<Integer> topicIds = newArrayList(1, 2);
+
+    // when
+    var result = topicEnrichmentService.enrichTopicIdsWithTopicData(topicIds);
+
+    // then
+    assertThat(result).isEmpty();
+  }
+
+  @Test
+  void enrichTopicIdsWithTopicData_Should_ReturnEmptyListIfTopicIdDoNotMatch() {
+    // given
+    when(topicService.getAllTopics()).thenReturn(
+        newArrayList(new TopicDTO().id(3L).name("third topic").description("desc"),
+            new TopicDTO().id(4L).name("fourth topic").description("desc")));
+    List<Integer> topicIds = newArrayList(1, 2);
+
+    // when
+    var result = topicEnrichmentService.enrichTopicIdsWithTopicData(topicIds);
+
+    // then
+    assertThat(result).isEmpty();
+  }
+}