diff --git a/backend/src/controllers/assignments.ts b/backend/src/controllers/assignments.ts
index 1520fc10..2750e3d8 100644
--- a/backend/src/controllers/assignments.ts
+++ b/backend/src/controllers/assignments.ts
@@ -1,6 +1,8 @@
 import { Request, Response } from 'express';
 import { createAssignment, getAllAssignments, getAssignment, getAssignmentsSubmissions } from '../services/assignments.js';
 import { AssignmentDTO } from '@dwengo-1/common/interfaces/assignment';
+import {requireFields} from "./error-helper";
+import {BadRequestException} from "../exceptions/bad-request-exception";
 
 // Typescript is annoying with parameter forwarding from class.ts
 interface AssignmentParams {
@@ -9,69 +11,55 @@ interface AssignmentParams {
 }
 
 export async function getAllAssignmentsHandler(req: Request<AssignmentParams>, res: Response): Promise<void> {
-    const classid = req.params.classid;
+    const classId = req.params.classid;
     const full = req.query.full === 'true';
+    requireFields({ classId });
 
-    const assignments = await getAllAssignments(classid, full);
+    const assignments = await getAllAssignments(classId, full);
 
-    res.json({
-        assignments: assignments,
-    });
+    res.json({ assignments });
 }
 
 export async function createAssignmentHandler(req: Request<AssignmentParams>, res: Response): Promise<void> {
     const classid = req.params.classid;
-    const assignmentData = req.body as AssignmentDTO;
+    const description = req.body.description;
+    const language = req.body.language;
+    const learningPath = req.body.learningPath;
+    const title = req.body.title;
 
-    if (!assignmentData.description || !assignmentData.language || !assignmentData.learningPath || !assignmentData.title) {
-        res.status(400).json({
-            error: 'Missing one or more required fields: title, description, learningPath, language',
-        });
-        return;
-    }
+    requireFields({ description, language, learningPath, title });
+    const assignmentData = req.body as AssignmentDTO;
 
     const assignment = await createAssignment(classid, assignmentData);
 
-    if (!assignment) {
-        res.status(500).json({ error: 'Could not create assignment ' });
-        return;
-    }
-
-    res.status(201).json(assignment);
+    res.json({ assignment });
 }
 
 export async function getAssignmentHandler(req: Request<AssignmentParams>, res: Response): Promise<void> {
     const id = Number(req.params.id);
     const classid = req.params.classid;
+    requireFields({ id, classid });
 
     if (isNaN(id)) {
-        res.status(400).json({ error: 'Assignment id must be a number' });
-        return;
+        throw new BadRequestException("Assignment id should be a number")
     }
 
     const assignment = await getAssignment(classid, id);
 
-    if (!assignment) {
-        res.status(404).json({ error: 'Assignment not found' });
-        return;
-    }
-
-    res.json(assignment);
+    res.json({ assignment });
 }
 
 export async function getAssignmentsSubmissionsHandler(req: Request<AssignmentParams>, res: Response): Promise<void> {
     const classid = req.params.classid;
     const assignmentNumber = Number(req.params.id);
     const full = req.query.full === 'true';
+    requireFields({ assignmentNumber, classid });
 
     if (isNaN(assignmentNumber)) {
-        res.status(400).json({ error: 'Assignment id must be a number' });
-        return;
+        throw new BadRequestException("Assignment id should be a number")
     }
 
     const submissions = await getAssignmentsSubmissions(classid, assignmentNumber, full);
 
-    res.json({
-        submissions: submissions,
-    });
+    res.json({ submissions });
 }
diff --git a/backend/src/services/assignments.ts b/backend/src/services/assignments.ts
index e86b69b2..fa8e2380 100644
--- a/backend/src/services/assignments.ts
+++ b/backend/src/services/assignments.ts
@@ -3,15 +3,12 @@ import { mapToAssignment, mapToAssignmentDTO, mapToAssignmentDTOId } from '../in
 import { mapToSubmissionDTO, mapToSubmissionDTOId } from '../interfaces/submission.js';
 import { AssignmentDTO } from '@dwengo-1/common/interfaces/assignment';
 import { SubmissionDTO, SubmissionDTOId } from '@dwengo-1/common/interfaces/submission';
-import { getLogger } from '../logging/initalize.js';
+import {fetchClass} from "./classes";
+import {Assignment} from "../entities/assignments/assignment.entity";
+import {NotFoundException} from "../exceptions/not-found-exception";
 
 export async function getAllAssignments(classid: string, full: boolean): Promise<AssignmentDTO[]> {
-    const classRepository = getClassRepository();
-    const cls = await classRepository.findById(classid);
-
-    if (!cls) {
-        return [];
-    }
+    const cls = await fetchClass(classid);
 
     const assignmentRepository = getAssignmentRepository();
     const assignments = await assignmentRepository.findAllAssignmentsInClass(cls);
@@ -23,43 +20,34 @@ export async function getAllAssignments(classid: string, full: boolean): Promise
     return assignments.map(mapToAssignmentDTOId);
 }
 
-export async function createAssignment(classid: string, assignmentData: AssignmentDTO): Promise<AssignmentDTO | null> {
-    const classRepository = getClassRepository();
-    const cls = await classRepository.findById(classid);
-
-    if (!cls) {
-        return null;
-    }
+export async function createAssignment(classid: string, assignmentData: AssignmentDTO): Promise<AssignmentDTO> {
+    const cls = await fetchClass(classid);
 
     const assignment = mapToAssignment(assignmentData, cls);
     const assignmentRepository = getAssignmentRepository();
 
-    try {
-        const newAssignment = assignmentRepository.create(assignment);
-        await assignmentRepository.save(newAssignment);
+    const newAssignment = assignmentRepository.create(assignment);
+    await assignmentRepository.save(newAssignment, {preventOverwrite: true});
+
+    return mapToAssignmentDTO(newAssignment);
 
-        return mapToAssignmentDTO(newAssignment);
-    } catch (e) {
-        getLogger().error(e);
-        return null;
-    }
 }
 
-export async function getAssignment(classid: string, id: number): Promise<AssignmentDTO | null> {
-    const classRepository = getClassRepository();
-    const cls = await classRepository.findById(classid);
-
-    if (!cls) {
-        return null;
-    }
+export async function fetchAssignment(classid: string, id: number): Promise<Assignment> {
+    const cls = await fetchClass(classid);
 
     const assignmentRepository = getAssignmentRepository();
     const assignment = await assignmentRepository.findByClassAndId(cls, id);
 
-    if (!assignment) {
-        return null;
+    if (!assignment){
+        throw new NotFoundException('Assignment with id not found');
     }
 
+    return assignment;
+}
+
+export async function getAssignment(classid: string, id: number): Promise<AssignmentDTO> {
+    const assignment = await fetchAssignment(classid, id);
     return mapToAssignmentDTO(assignment);
 }
 
@@ -68,23 +56,15 @@ export async function getAssignmentsSubmissions(
     assignmentNumber: number,
     full: boolean
 ): Promise<SubmissionDTO[] | SubmissionDTOId[]> {
-    const classRepository = getClassRepository();
-    const cls = await classRepository.findById(classid);
-
-    if (!cls) {
-        return [];
-    }
-
-    const assignmentRepository = getAssignmentRepository();
-    const assignment = await assignmentRepository.findByClassAndId(cls, assignmentNumber);
-
-    if (!assignment) {
-        return [];
-    }
+    const assignment = await fetchAssignment(classid, assignmentNumber);
 
     const groupRepository = getGroupRepository();
     const groups = await groupRepository.findAllGroupsForAssignment(assignment);
 
+    if (groups.length === 0){
+        throw new NotFoundException('No groups for assignment found');
+    }
+
     const submissionRepository = getSubmissionRepository();
     const submissions = (await Promise.all(groups.map(async (group) => submissionRepository.findAllSubmissionsForGroup(group)))).flat();