diff --git a/backend/.idea/workspace.xml b/backend/.idea/workspace.xml
index e60b4fc..c18727c 100644
--- a/backend/.idea/workspace.xml
+++ b/backend/.idea/workspace.xml
@@ -4,16 +4,8 @@
     <option name="autoReloadType" value="SELECTIVE" />
   </component>
   <component name="ChangeListManager">
-    <list default="true" id="3a869f59-290a-4ab2-b036-a878ce801bc4" name="Changes" comment="Testcases (and failing test fixes) of TaskgroupService">
-      <change afterPath="$PROJECT_DIR$/src/test/java/core/tasks/TaskServiceTest.java" afterDir="false" />
+    <list default="true" id="3a869f59-290a-4ab2-b036-a878ce801bc4" name="Changes" comment="Use @Sql instead of persit()">
       <change beforePath="$PROJECT_DIR$/.idea/workspace.xml" beforeDir="false" afterPath="$PROJECT_DIR$/.idea/workspace.xml" afterDir="false" />
-      <change beforePath="$PROJECT_DIR$/src/main/java/core/api/models/timemanager/tasks/TaskFieldInfo.java" beforeDir="false" afterPath="$PROJECT_DIR$/src/main/java/core/api/models/timemanager/tasks/TaskFieldInfo.java" afterDir="false" />
-      <change beforePath="$PROJECT_DIR$/src/main/java/core/entities/timemanager/Task.java" beforeDir="false" afterPath="$PROJECT_DIR$/src/main/java/core/entities/timemanager/Task.java" afterDir="false" />
-      <change beforePath="$PROJECT_DIR$/src/main/java/core/entities/timemanager/Taskgroup.java" beforeDir="false" afterPath="$PROJECT_DIR$/src/main/java/core/entities/timemanager/Taskgroup.java" afterDir="false" />
-      <change beforePath="$PROJECT_DIR$/src/main/java/core/services/ServiceExitCode.java" beforeDir="false" afterPath="$PROJECT_DIR$/src/main/java/core/services/ServiceExitCode.java" afterDir="false" />
-      <change beforePath="$PROJECT_DIR$/src/main/java/core/services/TaskService.java" beforeDir="false" afterPath="$PROJECT_DIR$/src/main/java/core/services/TaskService.java" afterDir="false" />
-      <change beforePath="$PROJECT_DIR$/src/test/resources/application.properties" beforeDir="false" afterPath="$PROJECT_DIR$/src/test/resources/application.properties" afterDir="false" />
-      <change beforePath="$PROJECT_DIR$/src/test/resources/taskRepositoryEntries.sql" beforeDir="false" afterPath="$PROJECT_DIR$/src/test/resources/taskRepositoryEntries.sql" afterDir="false" />
     </list>
     <option name="SHOW_DIALOG" value="false" />
     <option name="HIGHLIGHT_CONFLICTS" value="true" />
@@ -32,7 +24,7 @@
   <component name="Git.Settings">
     <option name="RECENT_BRANCH_BY_REPOSITORY">
       <map>
-        <entry key="$PROJECT_DIR$/.." value="master" />
+        <entry key="$PROJECT_DIR$/.." value="test-failing" />
       </map>
     </option>
     <option name="RECENT_GIT_ROOT_PATH" value="$PROJECT_DIR$/.." />
@@ -93,69 +85,6 @@
     </key>
   </component>
   <component name="RunManager" selected="JUnit.TaskgroupServiceTest">
-    <configuration name="TaskRepositoryTest.deleteByTaskID" type="JUnit" factoryName="JUnit" temporary="true" nameIsGenerated="true">
-      <module name="demo" />
-      <extension name="coverage">
-        <pattern>
-          <option name="PATTERN" value="core.tasks.*" />
-          <option name="ENABLED" value="true" />
-        </pattern>
-      </extension>
-      <option name="PACKAGE_NAME" value="core.tasks" />
-      <option name="MAIN_CLASS_NAME" value="core.tasks.TaskRepositoryTest" />
-      <option name="METHOD_NAME" value="deleteByTaskID" />
-      <option name="TEST_OBJECT" value="method" />
-      <method v="2">
-        <option name="Make" enabled="true" />
-      </method>
-    </configuration>
-    <configuration name="TaskServiceTest" type="JUnit" factoryName="JUnit" temporary="true" nameIsGenerated="true">
-      <module name="demo" />
-      <extension name="coverage">
-        <pattern>
-          <option name="PATTERN" value="core.tasks.*" />
-          <option name="ENABLED" value="true" />
-        </pattern>
-      </extension>
-      <option name="PACKAGE_NAME" value="core.tasks" />
-      <option name="MAIN_CLASS_NAME" value="core.tasks.TaskServiceTest" />
-      <option name="TEST_OBJECT" value="class" />
-      <method v="2">
-        <option name="Make" enabled="true" />
-      </method>
-    </configuration>
-    <configuration name="TaskServiceTest.createTask" type="JUnit" factoryName="JUnit" temporary="true" nameIsGenerated="true">
-      <module name="demo" />
-      <extension name="coverage">
-        <pattern>
-          <option name="PATTERN" value="core.tasks.*" />
-          <option name="ENABLED" value="true" />
-        </pattern>
-      </extension>
-      <option name="PACKAGE_NAME" value="core.tasks" />
-      <option name="MAIN_CLASS_NAME" value="core.tasks.TaskServiceTest" />
-      <option name="METHOD_NAME" value="createTask" />
-      <option name="TEST_OBJECT" value="method" />
-      <method v="2">
-        <option name="Make" enabled="true" />
-      </method>
-    </configuration>
-    <configuration name="TaskServiceTest.deleteTask" type="JUnit" factoryName="JUnit" temporary="true" nameIsGenerated="true">
-      <module name="demo" />
-      <extension name="coverage">
-        <pattern>
-          <option name="PATTERN" value="core.tasks.*" />
-          <option name="ENABLED" value="true" />
-        </pattern>
-      </extension>
-      <option name="PACKAGE_NAME" value="core.tasks" />
-      <option name="MAIN_CLASS_NAME" value="core.tasks.TaskServiceTest" />
-      <option name="METHOD_NAME" value="deleteTask" />
-      <option name="TEST_OBJECT" value="method" />
-      <method v="2">
-        <option name="Make" enabled="true" />
-      </method>
-    </configuration>
     <configuration name="TaskgroupServiceTest" type="JUnit" factoryName="JUnit" temporary="true" nameIsGenerated="true">
       <module name="demo" />
       <extension name="coverage">
@@ -171,6 +100,70 @@
         <option name="Make" enabled="true" />
       </method>
     </configuration>
+    <configuration name="TaskgroupServiceTest.deleteTaskgroup" type="JUnit" factoryName="JUnit" temporary="true" nameIsGenerated="true">
+      <module name="demo" />
+      <extension name="coverage">
+        <pattern>
+          <option name="PATTERN" value="core.taskgroups.*" />
+          <option name="ENABLED" value="true" />
+        </pattern>
+      </extension>
+      <option name="PACKAGE_NAME" value="core.taskgroups" />
+      <option name="MAIN_CLASS_NAME" value="core.taskgroups.TaskgroupServiceTest" />
+      <option name="METHOD_NAME" value="deleteTaskgroup" />
+      <option name="TEST_OBJECT" value="method" />
+      <method v="2">
+        <option name="Make" enabled="true" />
+      </method>
+    </configuration>
+    <configuration name="TaskgroupServiceTest.deleteTaskgroupByUser" type="JUnit" factoryName="JUnit" temporary="true" nameIsGenerated="true">
+      <module name="demo" />
+      <extension name="coverage">
+        <pattern>
+          <option name="PATTERN" value="core.taskgroups.*" />
+          <option name="ENABLED" value="true" />
+        </pattern>
+      </extension>
+      <option name="PACKAGE_NAME" value="core.taskgroups" />
+      <option name="MAIN_CLASS_NAME" value="core.taskgroups.TaskgroupServiceTest" />
+      <option name="METHOD_NAME" value="deleteTaskgroupByUser" />
+      <option name="TEST_OBJECT" value="method" />
+      <method v="2">
+        <option name="Make" enabled="true" />
+      </method>
+    </configuration>
+    <configuration name="TaskgroupServiceTest.getTaskgroupByIDAndUsername" type="JUnit" factoryName="JUnit" temporary="true" nameIsGenerated="true">
+      <module name="demo" />
+      <extension name="coverage">
+        <pattern>
+          <option name="PATTERN" value="core.taskgroups.*" />
+          <option name="ENABLED" value="true" />
+        </pattern>
+      </extension>
+      <option name="PACKAGE_NAME" value="core.taskgroups" />
+      <option name="MAIN_CLASS_NAME" value="core.taskgroups.TaskgroupServiceTest" />
+      <option name="METHOD_NAME" value="getTaskgroupByIDAndUsername" />
+      <option name="TEST_OBJECT" value="method" />
+      <method v="2">
+        <option name="Make" enabled="true" />
+      </method>
+    </configuration>
+    <configuration name="TaskgroupServiceTest.getTopTaskgroupsByUser" type="JUnit" factoryName="JUnit" temporary="true" nameIsGenerated="true">
+      <module name="demo" />
+      <extension name="coverage">
+        <pattern>
+          <option name="PATTERN" value="core.taskgroups.*" />
+          <option name="ENABLED" value="true" />
+        </pattern>
+      </extension>
+      <option name="PACKAGE_NAME" value="core.taskgroups" />
+      <option name="MAIN_CLASS_NAME" value="core.taskgroups.TaskgroupServiceTest" />
+      <option name="METHOD_NAME" value="getTopTaskgroupsByUser" />
+      <option name="TEST_OBJECT" value="method" />
+      <method v="2">
+        <option name="Make" enabled="true" />
+      </method>
+    </configuration>
     <configuration name="DemoApplication" type="SpringBootApplicationConfigurationType" factoryName="Spring Boot" nameIsGenerated="true">
       <module name="demo" />
       <option name="SPRING_BOOT_MAIN_CLASS" value="core.DemoApplication" />
@@ -181,10 +174,10 @@
     <recent_temporary>
       <list>
         <item itemvalue="JUnit.TaskgroupServiceTest" />
-        <item itemvalue="JUnit.TaskServiceTest" />
-        <item itemvalue="JUnit.TaskServiceTest.createTask" />
-        <item itemvalue="JUnit.TaskServiceTest.deleteTask" />
-        <item itemvalue="JUnit.TaskRepositoryTest.deleteByTaskID" />
+        <item itemvalue="JUnit.TaskgroupServiceTest.getTaskgroupByIDAndUsername" />
+        <item itemvalue="JUnit.TaskgroupServiceTest.deleteTaskgroupByUser" />
+        <item itemvalue="JUnit.TaskgroupServiceTest.getTopTaskgroupsByUser" />
+        <item itemvalue="JUnit.TaskgroupServiceTest.deleteTaskgroup" />
       </list>
     </recent_temporary>
   </component>
@@ -222,7 +215,7 @@
       <workItem from="1699466564154" duration="6646000" />
       <workItem from="1699473376129" duration="1423000" />
       <workItem from="1699639316405" duration="9267000" />
-      <workItem from="1699684493731" duration="7709000" />
+      <workItem from="1699684493731" duration="1121000" />
     </task>
     <task id="LOCAL-00001" summary="Structure Taskgroups in Hierarchies">
       <option name="closed" value="true" />
@@ -456,21 +449,14 @@
       <option name="project" value="LOCAL" />
       <updated>1699646291964</updated>
     </task>
-    <task id="LOCAL-00030" summary="Testcases (and failing test fixes) of TaskgroupService">
-      <option name="closed" value="true" />
-      <created>1699685656297</created>
-      <option name="number" value="00030" />
-      <option name="presentableId" value="LOCAL-00030" />
-      <option name="project" value="LOCAL" />
-      <updated>1699685656297</updated>
-    </task>
-    <option name="localTasksCounter" value="31" />
+    <option name="localTasksCounter" value="30" />
     <servers />
   </component>
   <component name="TypeScriptGeneratedFilesManager">
     <option name="version" value="3" />
   </component>
   <component name="VcsManagerConfiguration">
+    <MESSAGE value="Delete and clear Tasks (Frontend)" />
     <MESSAGE value="Define Entity BasicTaskSchedule and Taskcontroller" />
     <MESSAGE value="Delete Schedules" />
     <MESSAGE value="Deliver Schedule Path Info when fetching Schedules" />
@@ -495,8 +481,7 @@
     <MESSAGE value="Test TaskRepository" />
     <MESSAGE value="Initialize Testing of Testservice" />
     <MESSAGE value="Use @Sql instead of persit()" />
-    <MESSAGE value="Testcases (and failing test fixes) of TaskgroupService" />
-    <option name="LAST_COMMIT_MESSAGE" value="Testcases (and failing test fixes) of TaskgroupService" />
+    <option name="LAST_COMMIT_MESSAGE" value="Use @Sql instead of persit()" />
   </component>
   <component name="XDebuggerManager">
     <breakpoint-manager>
@@ -521,11 +506,6 @@
           <line>57</line>
           <option name="timeStamp" value="12" />
         </line-breakpoint>
-        <line-breakpoint enabled="true" type="java-line">
-          <url>file://$PROJECT_DIR$/src/test/java/core/tasks/TaskServiceTest.java</url>
-          <line>188</line>
-          <option name="timeStamp" value="23" />
-        </line-breakpoint>
       </breakpoints>
     </breakpoint-manager>
   </component>
diff --git a/backend/src/test/java/core/taskgroups/TaskgroupServiceTest.java b/backend/src/test/java/core/taskgroups/TaskgroupServiceTest.java
index d9d046b..eef487c 100644
--- a/backend/src/test/java/core/taskgroups/TaskgroupServiceTest.java
+++ b/backend/src/test/java/core/taskgroups/TaskgroupServiceTest.java
@@ -25,8 +25,10 @@ import org.springframework.boot.test.context.SpringBootTest;
 import org.springframework.test.context.jdbc.Sql;
 import org.springframework.test.context.jdbc.SqlGroup;
 import org.springframework.test.context.junit.jupiter.SpringExtension;
+import org.springframework.test.context.junit4.SpringRunner;
 
 import javax.persistence.EntityManager;
+import javax.transaction.Transactional;
 import java.util.List;
 import java.util.NoSuchElementException;
 import java.util.Optional;
@@ -35,6 +37,7 @@ import static org.assertj.core.api.AssertionsForClassTypes.assertThat;
 import static org.junit.jupiter.api.Assertions.*;
 
 @SpringBootTest
+@Transactional
 public class TaskgroupServiceTest {
 
     @Autowired