diff --git a/backend/src/controllers/auth.ts b/backend/src/controllers/auth.ts
index d3f3affb..b87eaf7b 100644
--- a/backend/src/controllers/auth.ts
+++ b/backend/src/controllers/auth.ts
@@ -1,16 +1,16 @@
 import { envVars, getEnvVar } from '../util/envVars.js';
 
-type FrontendIdpConfig = {
+interface FrontendIdpConfig {
     authority: string;
     clientId: string;
     scope: string;
     responseType: string;
-};
+}
 
-type FrontendAuthConfig = {
+interface FrontendAuthConfig {
     student: FrontendIdpConfig;
     teacher: FrontendIdpConfig;
-};
+}
 
 const SCOPE = 'openid profile email';
 const RESPONSE_TYPE = 'code';
diff --git a/backend/src/controllers/learning-objects.ts b/backend/src/controllers/learning-objects.ts
index 6e331ff3..14d200ce 100644
--- a/backend/src/controllers/learning-objects.ts
+++ b/backend/src/controllers/learning-objects.ts
@@ -13,7 +13,7 @@ function getLearningObjectIdentifierFromRequest(req: Request): LearningObjectIde
         throw new BadRequestException('HRUID is required.');
     }
     return {
-        hruid: req.params.hruid as string,
+        hruid: req.params.hruid,
         language: (req.query.language || getEnvVar(envVars.FallbackLanguage)) as Language,
         version: parseInt(req.query.version as string),
     };
@@ -24,7 +24,7 @@ function getLearningPathIdentifierFromRequest(req: Request): LearningPathIdentif
         throw new BadRequestException('HRUID is required.');
     }
     return {
-        hruid: req.params.hruid as string,
+        hruid: req.params.hruid,
         language: (req.query.language as Language) || FALLBACK_LANG,
     };
 }
diff --git a/backend/src/controllers/teachers.ts b/backend/src/controllers/teachers.ts
index e5f1fc87..4bf7eb53 100644
--- a/backend/src/controllers/teachers.ts
+++ b/backend/src/controllers/teachers.ts
@@ -85,7 +85,7 @@ export async function deleteTeacherHandler(req: Request, res: Response): Promise
 
 export async function getTeacherClassHandler(req: Request, res: Response): Promise<void> {
     try {
-        const username = req.params.username as string;
+        const username = req.params.username;
         const full = req.query.full === 'true';
 
         if (!username) {
@@ -104,7 +104,7 @@ export async function getTeacherClassHandler(req: Request, res: Response): Promi
 
 export async function getTeacherStudentHandler(req: Request, res: Response): Promise<void> {
     try {
-        const username = req.params.username as string;
+        const username = req.params.username;
         const full = req.query.full === 'true';
 
         if (!username) {
@@ -123,7 +123,7 @@ export async function getTeacherStudentHandler(req: Request, res: Response): Pro
 
 export async function getTeacherQuestionHandler(req: Request, res: Response): Promise<void> {
     try {
-        const username = req.params.username as string;
+        const username = req.params.username;
         const full = req.query.full === 'true';
 
         if (!username) {
diff --git a/backend/src/controllers/users.ts b/backend/src/controllers/users.ts
index 7706e2ee..255db93a 100644
--- a/backend/src/controllers/users.ts
+++ b/backend/src/controllers/users.ts
@@ -24,7 +24,7 @@ export async function getAllUsersHandler<T extends User>(req: Request, res: Resp
 
 export async function getUserHandler<T extends User>(req: Request, res: Response, service: UserService<T>): Promise<void> {
     try {
-        const username = req.params.username as string;
+        const username = req.params.username;
 
         if (!username) {
             res.status(400).json({ error: 'Missing required field: username' });
diff --git a/backend/src/interfaces/learning-content.ts b/backend/src/interfaces/learning-content.ts
index 51474917..693aec37 100644
--- a/backend/src/interfaces/learning-content.ts
+++ b/backend/src/interfaces/learning-content.ts
@@ -58,7 +58,7 @@ export interface EducationalGoal {
 
 export interface ReturnValue {
     callback_url: string;
-    callback_schema: Record<string, any>;
+    callback_schema: Record<string, unknown>;
 }
 
 export interface LearningObjectMetadata {
diff --git a/backend/src/middleware/auth/authentication-info.d.ts b/backend/src/middleware/auth/authentication-info.d.ts
index 4b060dfa..e8f0d48c 100644
--- a/backend/src/middleware/auth/authentication-info.d.ts
+++ b/backend/src/middleware/auth/authentication-info.d.ts
@@ -1,11 +1,11 @@
 /**
  * Object with information about the user who is currently logged in.
  */
-export type AuthenticationInfo = {
+export interface AuthenticationInfo {
     accountType: 'student' | 'teacher';
     username: string;
     name?: string;
     firstName?: string;
     lastName?: string;
     email?: string;
-};
+}
diff --git a/backend/src/services/learning-objects/database-learning-object-provider.ts b/backend/src/services/learning-objects/database-learning-object-provider.ts
index 03dbfdff..a8055f2c 100644
--- a/backend/src/services/learning-objects/database-learning-object-provider.ts
+++ b/backend/src/services/learning-objects/database-learning-object-provider.ts
@@ -1,7 +1,6 @@
 import { LearningObjectProvider } from './learning-object-provider.js';
 import { FilteredLearningObject, LearningObjectIdentifier, LearningPathIdentifier } from '../../interfaces/learning-content.js';
 import { getLearningObjectRepository, getLearningPathRepository } from '../../data/repositories.js';
-import { Language } from '../../entities/content/language.js';
 import { LearningObject } from '../../entities/content/learning-object.entity.js';
 import { getUrlStringForLearningObject } from '../../util/links.js';
 import processingService from './processing/processing-service.js';
@@ -44,7 +43,7 @@ function convertLearningObject(learningObject: LearningObject | null): FilteredL
 async function findLearningObjectEntityById(id: LearningObjectIdentifier): Promise<LearningObject | null> {
     const learningObjectRepo = getLearningObjectRepository();
 
-    return learningObjectRepo.findLatestByHruidAndLanguage(id.hruid, id.language as Language);
+    return learningObjectRepo.findLatestByHruidAndLanguage(id.hruid, id.language);
 }
 
 /**
@@ -65,7 +64,7 @@ const databaseLearningObjectProvider: LearningObjectProvider = {
     async getLearningObjectHTML(id: LearningObjectIdentifier): Promise<string | null> {
         const learningObjectRepo = getLearningObjectRepository();
 
-        const learningObject = await learningObjectRepo.findLatestByHruidAndLanguage(id.hruid, id.language as Language);
+        const learningObject = await learningObjectRepo.findLatestByHruidAndLanguage(id.hruid, id.language);
         if (!learningObject) {
             return null;
         }
diff --git a/backend/src/services/learning-objects/processing/markdown/markdown-processor.ts b/backend/src/services/learning-objects/processing/markdown/markdown-processor.ts
index 77673cbf..dbbf2a37 100644
--- a/backend/src/services/learning-objects/processing/markdown/markdown-processor.ts
+++ b/backend/src/services/learning-objects/processing/markdown/markdown-processor.ts
@@ -8,6 +8,7 @@ import { DwengoContentType } from '../content-type.js';
 import dwengoMarkedRenderer from './dwengo-marked-renderer.js';
 import { StringProcessor } from '../string-processor.js';
 import { ProcessingError } from '../processing-error.js';
+import { YAMLException } from 'js-yaml';
 
 class MarkdownProcessor extends StringProcessor {
     constructor() {
@@ -19,8 +20,12 @@ class MarkdownProcessor extends StringProcessor {
             marked.use({ renderer: dwengoMarkedRenderer });
             const html = marked(mdText, { async: false });
             return this.replaceLinks(html); // Replace html image links path
-        } catch (e: any) {
-            throw new ProcessingError(e.message);
+        } catch (e: unknown) {
+            if (e instanceof YAMLException) {
+                throw new ProcessingError(e.message);
+            }
+
+            throw new ProcessingError('Unknown error while processing markdown: ' + e);
         }
     }
 
diff --git a/backend/src/services/learning-objects/processing/processing-service.ts b/backend/src/services/learning-objects/processing/processing-service.ts
index a6c662cc..f731eb5d 100644
--- a/backend/src/services/learning-objects/processing/processing-service.ts
+++ b/backend/src/services/learning-objects/processing/processing-service.ts
@@ -21,7 +21,7 @@ const EMBEDDED_LEARNING_OBJECT_PLACEHOLDER = /<learning-object hruid="([^"]+)" l
 const LEARNING_OBJECT_DOES_NOT_EXIST = "<div class='non-existing-learning-object' />";
 
 class ProcessingService {
-    private processors!: Map<DwengoContentType, Processor<any>>;
+    private processors!: Map<DwengoContentType, Processor<DwengoContentType>>;
 
     constructor() {
         const processors = [
diff --git a/backend/src/services/learning-paths/database-learning-path-provider.ts b/backend/src/services/learning-paths/database-learning-path-provider.ts
index ed721517..c8ab41ca 100644
--- a/backend/src/services/learning-paths/database-learning-path-provider.ts
+++ b/backend/src/services/learning-paths/database-learning-path-provider.ts
@@ -25,7 +25,7 @@ async function getLearningObjectsForNodes(nodes: LearningPathNode[]): Promise<Ma
                         version: node.version,
                         language: node.language,
                     })
-                    .then((learningObject) => <[LearningPathNode, FilteredLearningObject | null]>[node, learningObject])
+                    .then((learningObject) => ([node, learningObject] as [LearningPathNode, FilteredLearningObject | null]))
             )
         )
     );
diff --git a/backend/src/sqlite-autoincrement-workaround.ts b/backend/src/sqlite-autoincrement-workaround.ts
index a5c20dfd..29d02ffc 100644
--- a/backend/src/sqlite-autoincrement-workaround.ts
+++ b/backend/src/sqlite-autoincrement-workaround.ts
@@ -27,14 +27,14 @@ export class SqliteAutoincrementSubscriber implements EventSubscriber {
 
         for (const prop of Object.values(args.meta.properties)) {
             const property = prop as EntityProperty<T>;
-            if (property.primary && property.autoincrement && !(args.entity as Record<string, any>)[property.name]) {
+            if (property.primary && property.autoincrement && !(args.entity as Record<string, unknown>)[property.name]) {
                 // Obtain and increment sequence number of this entity.
                 const propertyKey = args.meta.class.name + '.' + property.name;
                 const nextSeqNumber = this.sequenceNumbersForEntityType.get(propertyKey) || 0;
                 this.sequenceNumbersForEntityType.set(propertyKey, nextSeqNumber + 1);
 
                 // Set the property accordingly.
-                (args.entity as Record<string, any>)[property.name] = nextSeqNumber + 1;
+                (args.entity as Record<string, unknown>)[property.name] = nextSeqNumber + 1;
             }
         }
     }
diff --git a/backend/src/util/api-helper.ts b/backend/src/util/api-helper.ts
index fff7a6a1..9aac5bd1 100644
--- a/backend/src/util/api-helper.ts
+++ b/backend/src/util/api-helper.ts
@@ -1,5 +1,6 @@
 import axios, { AxiosRequestConfig } from 'axios';
 import { getLogger, Logger } from '../logging/initalize.js';
+import { LearningObjectIdentifier } from '../interfaces/learning-content.js';
 
 const logger: Logger = getLogger();
 
@@ -17,8 +18,8 @@ export async function fetchWithLogging<T>(
     url: string,
     description: string,
     options?: {
-        params?: Record<string, any>;
-        query?: Record<string, any>;
+        params?: Record<string, unknown> | LearningObjectIdentifier;
+        query?: Record<string, unknown>;
         responseType?: 'json' | 'text';
     }
 ): Promise<T | null> {
@@ -26,18 +27,21 @@ export async function fetchWithLogging<T>(
         const config: AxiosRequestConfig = options || {};
         const response = await axios.get<T>(url, config);
         return response.data;
-    } catch (error: any) {
-        if (error.response) {
-            if (error.response.status === 404) {
-                logger.debug(`❌ ERROR: ${description} not found (404) at "${url}".`);
+    } catch (error: unknown) {
+        if (axios.isAxiosError(error)) {
+            if (error.response) {
+                if (error.response.status === 404) {
+                    logger.debug(`❌ ERROR: ${description} not found (404) at "${url}".`);
+                } else {
+                    logger.debug(
+                        `❌ ERROR: Failed to fetch ${description}. Status: ${error.response.status} - ${error.response.statusText} (URL: "${url}")`
+                    );
+                }
             } else {
-                logger.debug(
-                    `❌ ERROR: Failed to fetch ${description}. Status: ${error.response.status} - ${error.response.statusText} (URL: "${url}")`
-                );
+                logger.debug(`❌ ERROR: Network or unexpected error when fetching ${description}:`, error.message);
             }
-        } else {
-            logger.debug(`❌ ERROR: Network or unexpected error when fetching ${description}:`, error.message);
         }
+        logger.error(`❌ ERROR: Unknown error while fetching ${description}.`, error);
         return null;
     }
 }
diff --git a/backend/src/util/envVars.ts b/backend/src/util/envVars.ts
index 15ad5928..aed0bebd 100644
--- a/backend/src/util/envVars.ts
+++ b/backend/src/util/envVars.ts
@@ -5,7 +5,7 @@ const STUDENT_IDP_PREFIX = IDP_PREFIX + 'STUDENT_';
 const TEACHER_IDP_PREFIX = IDP_PREFIX + 'TEACHER_';
 const CORS_PREFIX = PREFIX + 'CORS_';
 
-type EnvVar = { key: string; required?: boolean; defaultValue?: any };
+interface EnvVar { key: string; required?: boolean; defaultValue?: number | string | boolean }
 
 export const envVars: { [key: string]: EnvVar } = {
     Port: { key: PREFIX + 'PORT', defaultValue: 3000 },
@@ -44,7 +44,7 @@ export function getEnvVar(envVar: EnvVar): string {
     } else if (envVar.required) {
         throw new Error(`Missing environment variable: ${envVar.key}`);
     } else {
-        return envVar.defaultValue || '';
+        return String(envVar.defaultValue) || '';
     }
 }
 
diff --git a/backend/tests/test-assets/learning-objects/learning-object-example.d.ts b/backend/tests/test-assets/learning-objects/learning-object-example.d.ts
index 1d4009f8..5053ca75 100644
--- a/backend/tests/test-assets/learning-objects/learning-object-example.d.ts
+++ b/backend/tests/test-assets/learning-objects/learning-object-example.d.ts
@@ -1,8 +1,8 @@
 import { LearningObject } from '../../../src/entities/content/learning-object.entity';
 import { Attachment } from '../../../src/entities/content/attachment.entity';
 
-type LearningObjectExample = {
+interface LearningObjectExample {
     createLearningObject: () => LearningObject;
     createAttachment: { [key: string]: (owner: LearningObject) => Attachment };
     getHTMLRendering: () => string;
-};
+}
diff --git a/backend/tests/test-assets/learning-paths/learning-path-example.d.ts b/backend/tests/test-assets/learning-paths/learning-path-example.d.ts
index 9df3ba48..d8e94dc8 100644
--- a/backend/tests/test-assets/learning-paths/learning-path-example.d.ts
+++ b/backend/tests/test-assets/learning-paths/learning-path-example.d.ts
@@ -1,3 +1,3 @@
-type LearningPathExample = {
+interface LearningPathExample {
     createLearningPath: () => LearningPath;
-};
+}
diff --git a/backend/tests/test-assets/learning-paths/test-conditions-example.ts b/backend/tests/test-assets/learning-paths/test-conditions-example.ts
index 816cd735..b5e38c24 100644
--- a/backend/tests/test-assets/learning-paths/test-conditions-example.ts
+++ b/backend/tests/test-assets/learning-paths/test-conditions-example.ts
@@ -6,12 +6,12 @@ import { createLearningPathNode, createLearningPathTransition } from './learning
 import { LearningObject } from '../../../src/entities/content/learning-object.entity';
 import { envVars, getEnvVar } from '../../../src/util/envVars';
 
-export type ConditionTestLearningPathAndLearningObjects = {
+export interface ConditionTestLearningPathAndLearningObjects {
     branchingObject: LearningObject;
     extraExerciseObject: LearningObject;
     finalObject: LearningObject;
     learningPath: LearningPath;
-};
+}
 
 export function createConditionTestLearningPathAndLearningObjects(): ConditionTestLearningPathAndLearningObjects {
     const learningPath = new LearningPath();
diff --git a/backend/tests/test-utils/expectations.ts b/backend/tests/test-utils/expectations.ts
index 347f4b40..8f33bd8f 100644
--- a/backend/tests/test-utils/expectations.ts
+++ b/backend/tests/test-utils/expectations.ts
@@ -25,7 +25,7 @@ export function expectToBeCorrectEntity<T extends object>(actual: { entity: T; n
             expected.entity[property] !== undefined && // If we don't expect a certain value for a property, we assume it can be filled in by the database however it wants.
             typeof expected.entity[property] !== 'function' // Functions obviously are not persisted via the database
         ) {
-            if (!actual.entity.hasOwnProperty(property)) {
+            if (!Object.prototype.hasOwnProperty.call(actual.entity, property)) {
                 throw new AssertionError({
                     message: `${expected.name} has defined property ${property}, but ${actual.name} is missing it.`,
                 });
diff --git a/backend/tests/test_assets/assignments/assignments.testdata.ts b/backend/tests/test_assets/assignments/assignments.testdata.ts
index 7f909de4..5a5a3d5e 100644
--- a/backend/tests/test_assets/assignments/assignments.testdata.ts
+++ b/backend/tests/test_assets/assignments/assignments.testdata.ts
@@ -1,9 +1,9 @@
-import { Connection, EntityManager, IDatabaseDriver } from '@mikro-orm/core';
+import { EntityManager } from '@mikro-orm/core';
 import { Assignment } from '../../../src/entities/assignments/assignment.entity';
 import { Class } from '../../../src/entities/classes/class.entity';
 import { Language } from '../../../src/entities/content/language';
 
-export function makeTestAssignemnts(em: EntityManager<IDatabaseDriver<Connection>>, classes: Array<Class>): Array<Assignment> {
+export function makeTestAssignemnts(em: EntityManager, classes: Array<Class>): Array<Assignment> {
     const assignment01 = em.create(Assignment, {
         within: classes[0],
         id: 1,
diff --git a/backend/tests/test_assets/assignments/groups.testdata.ts b/backend/tests/test_assets/assignments/groups.testdata.ts
index 0e9ef201..199d6f48 100644
--- a/backend/tests/test_assets/assignments/groups.testdata.ts
+++ b/backend/tests/test_assets/assignments/groups.testdata.ts
@@ -1,13 +1,9 @@
-import { Connection, EntityManager, IDatabaseDriver } from '@mikro-orm/core';
+import { EntityManager } from '@mikro-orm/core';
 import { Group } from '../../../src/entities/assignments/group.entity';
 import { Assignment } from '../../../src/entities/assignments/assignment.entity';
 import { Student } from '../../../src/entities/users/student.entity';
 
-export function makeTestGroups(
-    em: EntityManager<IDatabaseDriver<Connection>>,
-    students: Array<Student>,
-    assignments: Array<Assignment>
-): Array<Group> {
+export function makeTestGroups(em: EntityManager, students: Array<Student>, assignments: Array<Assignment>): Array<Group> {
     const group01 = em.create(Group, {
         assignment: assignments[0],
         groupNumber: 1,
diff --git a/backend/tests/test_assets/assignments/submission.testdata.ts b/backend/tests/test_assets/assignments/submission.testdata.ts
index 95dd65df..7b56a6cb 100644
--- a/backend/tests/test_assets/assignments/submission.testdata.ts
+++ b/backend/tests/test_assets/assignments/submission.testdata.ts
@@ -1,14 +1,10 @@
-import { Connection, EntityManager, IDatabaseDriver } from '@mikro-orm/core';
+import { EntityManager } from '@mikro-orm/core';
 import { Submission } from '../../../src/entities/assignments/submission.entity';
 import { Language } from '../../../src/entities/content/language';
 import { Student } from '../../../src/entities/users/student.entity';
 import { Group } from '../../../src/entities/assignments/group.entity';
 
-export function makeTestSubmissions(
-    em: EntityManager<IDatabaseDriver<Connection>>,
-    students: Array<Student>,
-    groups: Array<Group>
-): Array<Submission> {
+export function makeTestSubmissions(em: EntityManager, students: Array<Student>, groups: Array<Group>): Array<Submission> {
     const submission01 = em.create(Submission, {
         learningObjectHruid: 'id03',
         learningObjectLanguage: Language.English,
diff --git a/backend/tests/test_assets/classes/class-join-requests.testdata.ts b/backend/tests/test_assets/classes/class-join-requests.testdata.ts
index 8d9e328f..f0e151ca 100644
--- a/backend/tests/test_assets/classes/class-join-requests.testdata.ts
+++ b/backend/tests/test_assets/classes/class-join-requests.testdata.ts
@@ -1,13 +1,9 @@
-import { Connection, EntityManager, IDatabaseDriver } from '@mikro-orm/core';
+import { EntityManager } from '@mikro-orm/core';
 import { ClassJoinRequest, ClassJoinRequestStatus } from '../../../src/entities/classes/class-join-request.entity';
 import { Student } from '../../../src/entities/users/student.entity';
 import { Class } from '../../../src/entities/classes/class.entity';
 
-export function makeTestClassJoinRequests(
-    em: EntityManager<IDatabaseDriver<Connection>>,
-    students: Array<Student>,
-    classes: Array<Class>
-): Array<ClassJoinRequest> {
+export function makeTestClassJoinRequests(em: EntityManager, students: Array<Student>, classes: Array<Class>): Array<ClassJoinRequest> {
     const classJoinRequest01 = em.create(ClassJoinRequest, {
         requester: students[4],
         class: classes[1],
diff --git a/backend/tests/test_assets/classes/classes.testdata.ts b/backend/tests/test_assets/classes/classes.testdata.ts
index b3e98bc8..e122d084 100644
--- a/backend/tests/test_assets/classes/classes.testdata.ts
+++ b/backend/tests/test_assets/classes/classes.testdata.ts
@@ -1,9 +1,9 @@
-import { Connection, EntityManager, IDatabaseDriver } from '@mikro-orm/core';
+import { EntityManager } from '@mikro-orm/core';
 import { Class } from '../../../src/entities/classes/class.entity';
 import { Student } from '../../../src/entities/users/student.entity';
 import { Teacher } from '../../../src/entities/users/teacher.entity';
 
-export function makeTestClasses(em: EntityManager<IDatabaseDriver<Connection>>, students: Array<Student>, teachers: Array<Teacher>): Array<Class> {
+export function makeTestClasses(em: EntityManager, students: Array<Student>, teachers: Array<Teacher>): Array<Class> {
     const studentsClass01 = students.slice(0, 7);
     const teacherClass01: Array<Teacher> = teachers.slice(0, 1);
 
diff --git a/backend/tests/test_assets/classes/teacher-invitations.testdata.ts b/backend/tests/test_assets/classes/teacher-invitations.testdata.ts
index 84eeab01..35b471a4 100644
--- a/backend/tests/test_assets/classes/teacher-invitations.testdata.ts
+++ b/backend/tests/test_assets/classes/teacher-invitations.testdata.ts
@@ -1,13 +1,9 @@
-import { Connection, EntityManager, IDatabaseDriver } from '@mikro-orm/core';
+import { EntityManager } from '@mikro-orm/core';
 import { TeacherInvitation } from '../../../src/entities/classes/teacher-invitation.entity';
 import { Teacher } from '../../../src/entities/users/teacher.entity';
 import { Class } from '../../../src/entities/classes/class.entity';
 
-export function makeTestTeacherInvitations(
-    em: EntityManager<IDatabaseDriver<Connection>>,
-    teachers: Array<Teacher>,
-    classes: Array<Class>
-): Array<TeacherInvitation> {
+export function makeTestTeacherInvitations(em: EntityManager, teachers: Array<Teacher>, classes: Array<Class>): Array<TeacherInvitation> {
     const teacherInvitation01 = em.create(TeacherInvitation, {
         sender: teachers[1],
         receiver: teachers[0],
diff --git a/backend/tests/test_assets/content/attachments.testdata.ts b/backend/tests/test_assets/content/attachments.testdata.ts
index 9f690d9c..22242a77 100644
--- a/backend/tests/test_assets/content/attachments.testdata.ts
+++ b/backend/tests/test_assets/content/attachments.testdata.ts
@@ -1,8 +1,8 @@
-import { Connection, EntityManager, IDatabaseDriver } from '@mikro-orm/core';
+import { EntityManager } from '@mikro-orm/core';
 import { Attachment } from '../../../src/entities/content/attachment.entity';
 import { LearningObject } from '../../../src/entities/content/learning-object.entity';
 
-export function makeTestAttachments(em: EntityManager<IDatabaseDriver<Connection>>, learningObjects: Array<LearningObject>): Array<Attachment> {
+export function makeTestAttachments(em: EntityManager, learningObjects: Array<LearningObject>): Array<Attachment> {
     const attachment01 = em.create(Attachment, {
         learningObject: learningObjects[1],
         name: 'attachment01',
diff --git a/backend/tests/test_assets/content/learning-objects.testdata.ts b/backend/tests/test_assets/content/learning-objects.testdata.ts
index 17ed4f01..e45bdea0 100644
--- a/backend/tests/test_assets/content/learning-objects.testdata.ts
+++ b/backend/tests/test_assets/content/learning-objects.testdata.ts
@@ -1,9 +1,9 @@
-import { Connection, EntityManager, IDatabaseDriver } from '@mikro-orm/core';
+import { EntityManager } from '@mikro-orm/core';
 import { LearningObject, ReturnValue } from '../../../src/entities/content/learning-object.entity';
 import { Language } from '../../../src/entities/content/language';
 import { DwengoContentType } from '../../../src/services/learning-objects/processing/content-type';
 
-export function makeTestLearningObjects(em: EntityManager<IDatabaseDriver<Connection>>): Array<LearningObject> {
+export function makeTestLearningObjects(em: EntityManager): Array<LearningObject> {
     const returnValue: ReturnValue = new ReturnValue();
     returnValue.callbackSchema = '';
     returnValue.callbackUrl = '';
diff --git a/backend/tests/test_assets/content/learning-paths.testdata.ts b/backend/tests/test_assets/content/learning-paths.testdata.ts
index 10de885c..3b62b55c 100644
--- a/backend/tests/test_assets/content/learning-paths.testdata.ts
+++ b/backend/tests/test_assets/content/learning-paths.testdata.ts
@@ -1,10 +1,10 @@
-import { Connection, EntityManager, IDatabaseDriver } from '@mikro-orm/core';
+import { EntityManager } from '@mikro-orm/core';
 import { LearningPath } from '../../../src/entities/content/learning-path.entity';
 import { Language } from '../../../src/entities/content/language';
 import { LearningPathTransition } from '../../../src/entities/content/learning-path-transition.entity';
 import { LearningPathNode } from '../../../src/entities/content/learning-path-node.entity';
 
-export function makeTestLearningPaths(em: EntityManager<IDatabaseDriver<Connection>>): Array<LearningPath> {
+export function makeTestLearningPaths(em: EntityManager): Array<LearningPath> {
     const learningPathNode01: LearningPathNode = new LearningPathNode();
     const learningPathNode02: LearningPathNode = new LearningPathNode();
     const learningPathNode03: LearningPathNode = new LearningPathNode();
diff --git a/backend/tests/test_assets/questions/answers.testdata.ts b/backend/tests/test_assets/questions/answers.testdata.ts
index 20e816da..4332a70f 100644
--- a/backend/tests/test_assets/questions/answers.testdata.ts
+++ b/backend/tests/test_assets/questions/answers.testdata.ts
@@ -1,9 +1,9 @@
-import { Connection, EntityManager, IDatabaseDriver } from '@mikro-orm/core';
+import { EntityManager } from '@mikro-orm/core';
 import { Answer } from '../../../src/entities/questions/answer.entity';
 import { Teacher } from '../../../src/entities/users/teacher.entity';
 import { Question } from '../../../src/entities/questions/question.entity';
 
-export function makeTestAnswers(em: EntityManager<IDatabaseDriver<Connection>>, teachers: Array<Teacher>, questions: Array<Question>): Array<Answer> {
+export function makeTestAnswers(em: EntityManager, teachers: Array<Teacher>, questions: Array<Question>): Array<Answer> {
     const answer01 = em.create(Answer, {
         author: teachers[0],
         toQuestion: questions[1],
diff --git a/backend/tests/test_assets/questions/questions.testdata.ts b/backend/tests/test_assets/questions/questions.testdata.ts
index cea43e18..0c19109a 100644
--- a/backend/tests/test_assets/questions/questions.testdata.ts
+++ b/backend/tests/test_assets/questions/questions.testdata.ts
@@ -1,9 +1,9 @@
-import { Connection, EntityManager, IDatabaseDriver } from '@mikro-orm/core';
+import { EntityManager } from '@mikro-orm/core';
 import { Question } from '../../../src/entities/questions/question.entity';
 import { Language } from '../../../src/entities/content/language';
 import { Student } from '../../../src/entities/users/student.entity';
 
-export function makeTestQuestions(em: EntityManager<IDatabaseDriver<Connection>>, students: Array<Student>): Array<Question> {
+export function makeTestQuestions(em: EntityManager, students: Array<Student>): Array<Question> {
     const question01 = em.create(Question, {
         learningObjectLanguage: Language.English,
         learningObjectVersion: 1,
diff --git a/backend/tests/test_assets/users/students.testdata.ts b/backend/tests/test_assets/users/students.testdata.ts
index 61e0b590..aff29913 100644
--- a/backend/tests/test_assets/users/students.testdata.ts
+++ b/backend/tests/test_assets/users/students.testdata.ts
@@ -1,7 +1,7 @@
-import { Connection, EntityManager, IDatabaseDriver } from '@mikro-orm/core';
+import { EntityManager } from '@mikro-orm/core';
 import { Student } from '../../../src/entities/users/student.entity';
 
-export function makeTestStudents(em: EntityManager<IDatabaseDriver<Connection>>): Array<Student> {
+export function makeTestStudents(em: EntityManager): Array<Student> {
     const student01 = em.create(Student, {
         username: 'Noordkaap',
         firstName: 'Stijn',
diff --git a/backend/tests/test_assets/users/teachers.testdata.ts b/backend/tests/test_assets/users/teachers.testdata.ts
index d8985e44..7e519f7d 100644
--- a/backend/tests/test_assets/users/teachers.testdata.ts
+++ b/backend/tests/test_assets/users/teachers.testdata.ts
@@ -1,7 +1,7 @@
 import { Teacher } from '../../../src/entities/users/teacher.entity';
-import { Connection, EntityManager, IDatabaseDriver } from '@mikro-orm/core';
+import { EntityManager } from '@mikro-orm/core';
 
-export function makeTestTeachers(em: EntityManager<IDatabaseDriver<Connection>>): Array<Teacher> {
+export function makeTestTeachers(em: EntityManager): Array<Teacher> {
     const teacher01 = em.create(Teacher, {
         username: 'FooFighters',
         firstName: 'Dave',
diff --git a/eslint.config.ts b/eslint.config.ts
index 3596633a..bbc68665 100644
--- a/eslint.config.ts
+++ b/eslint.config.ts
@@ -34,6 +34,10 @@ export default [
         rules: {
             'consistent-return': 'off',
             '@typescript-eslint/consistent-return': 'off',
+            '@typescript-eslint/consistent-type-assertions': 'error',
+            '@typescript-eslint/consistent-type-definitions': 'error',
+            '@typescript-eslint/consistent-type-exports': 'off',
+            '@typescript-eslint/consistent-type-imports': 'off',
 
             '@typescript-eslint/explicit-function-return-type': 'warn',
 
@@ -58,12 +62,24 @@ export default [
                 }
             ],
 
+            'no-dupe-class-members': 'off',
+            '@typescript-eslint/no-dupe-class-members': 'off',
+            '@typescript-eslint/no-duplicate-enum-values': 'error',
+            'no-duplicate-imports': 'off',
+            '@typescript-eslint/no-duplicate-type-constituents': 'off',
+
             // 'no-empty-function': 'off',
             '@typescript-eslint/no-empty-function': 'error',
 
             'no-loop-func': 'off',
             '@typescript-eslint/no-loop-func': 'error',
 
+            '@typescript-eslint/no-type-alias': 'off',
+
+            '@typescript-eslint/no-unnecessary-type-arguments': 'error',
+            '@typescript-eslint/no-unnecessary-type-assertion': 'error',
+            '@typescript-eslint/no-unnecessary-type-constraint': 'error',
+            '@typescript-eslint/no-unnecessary-type-parameters': 'off',
             '@typescript-eslint/no-unsafe-function-type': 'error',
 
             'no-unused-expressions': 'off',
@@ -89,7 +105,6 @@ export default [
 
             'no-await-in-loop': 'warn',
             'no-constructor-return': 'error',
-            'no-duplicate-imports': 'error',
             'no-inner-declarations': 'error',
             'no-self-compare': 'error',
             'no-template-curly-in-string': 'error',
@@ -100,7 +115,6 @@ export default [
             'arrow-body-style': ['warn', 'as-needed'],
             'block-scoped-var': 'warn',
             'capitalized-comments': 'warn',
-            'consistent-return': 'warn',
             'consistent-this': 'error',
             curly: 'error',
             'default-case': 'error',