diff --git a/backend/src/controllers/learning-paths.ts b/backend/src/controllers/learning-paths.ts
index cb5ae07e..6fadb10d 100644
--- a/backend/src/controllers/learning-paths.ts
+++ b/backend/src/controllers/learning-paths.ts
@@ -23,9 +23,7 @@ export async function getLearningPaths(
             ? hruids.map(String)
             : [String(hruids)];
     } else if (themeKey) {
-        const theme = themes.find((t) => {
-            return t.title === themeKey;
-        });
+        const theme = themes.find((t) => t.title === themeKey);
         if (theme) {
             hruidList = theme.hruids;
         } else {
@@ -39,9 +37,7 @@ export async function getLearningPaths(
         res.json(searchResults);
         return;
     } else {
-        hruidList = themes.flatMap((theme) => {
-            return theme.hruids;
-        });
+        hruidList = themes.flatMap((theme) => theme.hruids);
     }
 
     const learningPaths = await learningPathService.fetchLearningPaths(
diff --git a/backend/src/services/learning-objects/attachment-service.ts b/backend/src/services/learning-objects/attachment-service.ts
index 2285ddfe..fb2b2dd2 100644
--- a/backend/src/services/learning-objects/attachment-service.ts
+++ b/backend/src/services/learning-objects/attachment-service.ts
@@ -12,9 +12,9 @@ const attachmentService = {
                 language: learningObjectId.language,
                 version: learningObjectId.version,
             }, attachmentName);
-        } else {
+        } 
             return attachmentRepo.findByMostRecentVersionOfLearningObjectAndName(learningObjectId.hruid, learningObjectId.language, attachmentName);
-        }
+        
     }
 }
 
diff --git a/backend/src/services/learning-objects/dwengo-api-learning-object-provider.ts b/backend/src/services/learning-objects/dwengo-api-learning-object-provider.ts
index 628f616c..ab914be4 100644
--- a/backend/src/services/learning-objects/dwengo-api-learning-object-provider.ts
+++ b/backend/src/services/learning-objects/dwengo-api-learning-object-provider.ts
@@ -68,23 +68,15 @@ async function fetchLearningObjects(
         const nodes: LearningObjectNode[] = learningPathResponse.data[0].nodes;
 
         if (!full) {
-            return nodes.map((node) => {
-                return node.learningobject_hruid;
-            });
+            return nodes.map((node) => node.learningobject_hruid);
         }
 
         return await Promise.all(
-            nodes.map(async (node) => {
-                return dwengoApiLearningObjectProvider.getLearningObjectById({
+            nodes.map(async (node) => dwengoApiLearningObjectProvider.getLearningObjectById({
                     hruid: node.learningobject_hruid,
                     language: learningPathId.language
-                });
-            })
-        ).then((objects) => {
-            return objects.filter((obj): obj is FilteredLearningObject => {
-                return obj !== null;
-            });
-        });
+                }))
+        ).then((objects) => objects.filter((obj): obj is FilteredLearningObject => obj !== null));
     } catch (error) {
         console.error('❌ Error fetching learning objects:', error);
         return [];
@@ -98,7 +90,7 @@ const dwengoApiLearningObjectProvider: LearningObjectProvider = {
     async getLearningObjectById(
         id: LearningObjectIdentifier
     ): Promise<FilteredLearningObject | null> {
-        let metadataUrl = `${DWENGO_API_BASE}/learningObject/getMetadata`;
+        const metadataUrl = `${DWENGO_API_BASE}/learningObject/getMetadata`;
         const metadata = await fetchWithLogging<LearningObjectMetadata>(
             metadataUrl,
             `Metadata for Learning Object HRUID "${id.hruid}" (language ${id.language})`,
diff --git a/backend/src/services/learning-objects/learning-object-service.ts b/backend/src/services/learning-objects/learning-object-service.ts
index 51152ec8..9dd327f0 100644
--- a/backend/src/services/learning-objects/learning-object-service.ts
+++ b/backend/src/services/learning-objects/learning-object-service.ts
@@ -11,9 +11,9 @@ import databaseLearningObjectProvider from "./database-learning-object-provider"
 function getProvider(id: LearningObjectIdentifier): LearningObjectProvider {
     if (id.hruid.startsWith(getEnvVar(EnvVars.UserContentPrefix))) {
         return databaseLearningObjectProvider;
-    } else {
+    } 
         return dwengoApiLearningObjectProvider;
-    }
+    
 }
 
 /**
diff --git a/backend/src/services/learning-objects/processing/extern/extern-processor.ts b/backend/src/services/learning-objects/processing/extern/extern-processor.ts
index aff26d45..68ec9899 100644
--- a/backend/src/services/learning-objects/processing/extern/extern-processor.ts
+++ b/backend/src/services/learning-objects/processing/extern/extern-processor.ts
@@ -22,7 +22,7 @@ class ExternProcessor extends StringProcessor {
 
         // If a seperate youtube-processor would be added, this code would need to move to that processor
         // Converts youtube urls to youtube-embed urls
-        let match = /(.*youtube.com\/)watch\?v=(.*)/.exec(externURL)
+        const match = /(.*youtube.com\/)watch\?v=(.*)/.exec(externURL)
         if (match) {
             externURL = match[1] + "embed/" + match[2];
         }
diff --git a/backend/src/services/learning-objects/processing/gift/gift-processor.ts b/backend/src/services/learning-objects/processing/gift/gift-processor.ts
index 5d20e99c..b6eba8ba 100644
--- a/backend/src/services/learning-objects/processing/gift/gift-processor.ts
+++ b/backend/src/services/learning-objects/processing/gift/gift-processor.ts
@@ -38,9 +38,9 @@ class GiftProcessor extends StringProcessor {
 
         let html = "<div class='learning-object-gift'>\n";
         let i = 1;
-        for (let question of quizQuestions) {
+        for (const question of quizQuestions) {
             html += `    <div class='gift-question' id='gift-q${i}'>\n`;
-            html += "        " + this.renderQuestion(question, i).replaceAll(/\n(.+)/g, "\n        $1"); // replace for indentation.
+            html += "        " + this.renderQuestion(question, i).replaceAll(/\n(.+)/g, "\n        $1"); // Replace for indentation.
             html += `    </div>\n`;
             i++;
         }
diff --git a/backend/src/services/learning-objects/processing/gift/question-renderers/multiple-choice-question-renderer.ts b/backend/src/services/learning-objects/processing/gift/question-renderers/multiple-choice-question-renderer.ts
index 6b6d8eea..bf1de8c4 100644
--- a/backend/src/services/learning-objects/processing/gift/question-renderers/multiple-choice-question-renderer.ts
+++ b/backend/src/services/learning-objects/processing/gift/question-renderers/multiple-choice-question-renderer.ts
@@ -11,7 +11,7 @@ export class MultipleChoiceQuestionRenderer extends GIFTQuestionRenderer<Multipl
             renderedHtml += `<p class='gift-stem' id='gift-q${questionNumber}-stem'>${question.stem.text}</p>\n`;
         }
         let i = 0;
-        for (let choice of question.choices) {
+        for (const choice of question.choices) {
             renderedHtml += `<div class="gift-choice-div">\n`;
             renderedHtml += `    <input type='radio' id='gift-q${questionNumber}-choice-${i}' name='gift-q${questionNumber}-choices' value="${i}"/>\n`;
             renderedHtml += `    <label for='gift-q${questionNumber}-choice-${i}'>${choice.text}</label>\n`;
diff --git a/backend/src/services/learning-objects/processing/image/block-image-processor.ts b/backend/src/services/learning-objects/processing/image/block-image-processor.ts
index cb488e92..7d578e1c 100644
--- a/backend/src/services/learning-objects/processing/image/block-image-processor.ts
+++ b/backend/src/services/learning-objects/processing/image/block-image-processor.ts
@@ -11,7 +11,7 @@ class BlockImageProcessor extends InlineImageProcessor {
     }
 
     override renderFn(imageUrl: string){
-        let inlineHtml = super.render(imageUrl);
+        const inlineHtml = super.render(imageUrl);
         return DOMPurify.sanitize(`<div>${inlineHtml}</div>`);
     }
 }
diff --git a/backend/src/services/learning-objects/processing/markdown/dwengo-marked-renderer.ts b/backend/src/services/learning-objects/processing/markdown/dwengo-marked-renderer.ts
index 04b15b94..d5324754 100644
--- a/backend/src/services/learning-objects/processing/markdown/dwengo-marked-renderer.ts
+++ b/backend/src/services/learning-objects/processing/markdown/dwengo-marked-renderer.ts
@@ -56,53 +56,53 @@ function extractLearningObjectIdFromHref(href: string): LearningObjectIdentifier
     },
 
     // When the syntax for a link is used => [text](href "title")
-    // render a custom link when the prefix for a learning object is used.
+    // Render a custom link when the prefix for a learning object is used.
     link(link: Link): string {
         const href = link.href;
         const title = link.title || "";
         const text = marked.parseInline(link.text); // There could for example be an image in the link.
 
         if (href.startsWith(prefixes.learningObject)) {
-            // link to learning-object
+            // Link to learning-object
             const learningObjectId = extractLearningObjectIdFromHref(href);
             return `<a href="${getUrlStringForLearningObjectHTML(learningObjectId)}" target="_blank" title="${title}">${text}</a>`;
-        } else {
-            // any other link
+        } 
+            // Any other link
             if (!isValidHttpUrl(href)) {
                 throw new ProcessingError("Link is not a valid HTTP URL!");
             }
             //<a href="https://kiks.ilabt.imec.be/hub/tmplogin?id=0101" title="Notebooks Werking"><img src="Knop.png" alt="" title="Knop"></a>
             return `<a href="${href}" target="_blank" title="${title}">${text}</a>`;
-        }
+        
     },
 
     // When the syntax for an image is used => ![text](href "title")
-    // render a learning object, pdf, audio or video if a prefix is used.
+    // Render a learning object, pdf, audio or video if a prefix is used.
     image(img: Image): string {
         const href = img.href;
         if (href.startsWith(prefixes.learningObject)) {
-            // embedded learning-object
+            // Embedded learning-object
             const learningObjectId = extractLearningObjectIdFromHref(href);
             return `
                 <learning-object hruid="${learningObjectId.hruid}" language="${learningObjectId.language}" version="${learningObjectId.version}"/>
             `; // Placeholder for the learning object since we cannot fetch its HTML here (this has to be a sync function!)
         } else if (href.startsWith(prefixes.pdf)) {
-            // embedded pdf
-            let proc = new PdfProcessor();
+            // Embedded pdf
+            const proc = new PdfProcessor();
             return proc.render(href.split(/\/(.+)/, 2)[1]);
         } else if (href.startsWith(prefixes.audio)) {
-            // embedded audio
-            let proc = new AudioProcessor();
+            // Embedded audio
+            const proc = new AudioProcessor();
             return proc.render(href.split(/\/(.+)/, 2)[1]);
         } else if (href.startsWith(prefixes.extern) || href.startsWith(prefixes.video) || href.startsWith(prefixes.notebook)) {
-            // embedded youtube video or notebook (or other extern content)
-            let proc = new ExternProcessor();
+            // Embedded youtube video or notebook (or other extern content)
+            const proc = new ExternProcessor();
             return proc.render(href.split(/\/(.+)/, 2)[1]);
-        } else {
-            // embedded image
-            let proc = new InlineImageProcessor();
+        } 
+            // Embedded image
+            const proc = new InlineImageProcessor();
             return proc.render(href)
-        }
+        
     },
 }
 
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 c20f08a3..58824c13 100644
--- a/backend/src/services/learning-objects/processing/markdown/markdown-processor.ts
+++ b/backend/src/services/learning-objects/processing/markdown/markdown-processor.ts
@@ -27,7 +27,7 @@ class MarkdownProcessor extends StringProcessor {
     }
 
     replaceLinks(html: string) {
-        let proc = new InlineImageProcessor();
+        const proc = new InlineImageProcessor();
         html = html.replace(/<img.*?src="(.*?)".*?(alt="(.*?)")?.*?(title="(.*?)")?.*?>/g, (
             match: string,
             src: string,
@@ -35,9 +35,7 @@ class MarkdownProcessor extends StringProcessor {
             altText: string,
             title: string,
             titleText: string
-        ) => {
-            return proc.render(src);
-        });
+        ) => proc.render(src));
         return html;
     }
 }
diff --git a/backend/src/services/learning-objects/processing/processing-service.ts b/backend/src/services/learning-objects/processing/processing-service.ts
index a9885718..c682de32 100644
--- a/backend/src/services/learning-objects/processing/processing-service.ts
+++ b/backend/src/services/learning-objects/processing/processing-service.ts
@@ -54,7 +54,7 @@ class ProcessingService {
         learningObject: LearningObject,
         fetchEmbeddedLearningObjects?: (loId: LearningObjectIdentifier) => Promise<LearningObject | null>
     ): Promise<string> {
-        let html = this.processors.get(learningObject.contentType)!.renderLearningObject(learningObject);
+        const html = this.processors.get(learningObject.contentType)!.renderLearningObject(learningObject);
         if (fetchEmbeddedLearningObjects) {
             // Replace all embedded learning objects.
             return replaceAsync(
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 b9fa9ff6..60edb98b 100644
--- a/backend/src/services/learning-paths/database-learning-path-provider.ts
+++ b/backend/src/services/learning-paths/database-learning-path-provider.ts
@@ -22,7 +22,7 @@ import {LearningPathTransition} from "../../entities/content/learning-path-trans
  */
 async function getLearningObjectsForNodes(nodes: LearningPathNode[]): Promise<Map<LearningPathNode, FilteredLearningObject>> {
     // Fetching the corresponding learning object for each of the nodes and creating a map that maps each node to
-    // its corresponding learning object.
+    // Its corresponding learning object.
     const nullableNodesToLearningObjects = new Map<LearningPathNode, FilteredLearningObject | null>(
         await Promise.all(
             nodes.map(node =>
@@ -58,7 +58,7 @@ async function convertLearningPath(learningPath: LearningPathEntity, order: numb
     const image = learningPath.image ? learningPath.image.toString("base64") : undefined;
 
     return {
-        _id: `${learningPath.hruid}/${learningPath.language}`, // for backwards compatibility with the original Dwengo API.
+        _id: `${learningPath.hruid}/${learningPath.language}`, // For backwards compatibility with the original Dwengo API.
         __order: order,
         hruid: learningPath.hruid,
         language: learningPath.language,
diff --git a/backend/src/services/learning-paths/learning-path-personalizing-service.ts b/backend/src/services/learning-paths/learning-path-personalizing-service.ts
index b7d1fe06..6cd8f610 100644
--- a/backend/src/services/learning-paths/learning-path-personalizing-service.ts
+++ b/backend/src/services/learning-paths/learning-path-personalizing-service.ts
@@ -43,7 +43,7 @@ function transitionPossible(transition: LearningPathTransition, submitted: objec
  */
 const learningPathPersonalizingService = {
     async calculatePersonalizedTrajectory(nodes: LearningPathNode[], pathFor: {student?: Student, group?: Group}): Promise<LearningPathNode[]> {
-        let trajectory: LearningPathNode[] = [];
+        const trajectory: LearningPathNode[] = [];
 
         // Always start with the start node.
         let currentNode = nodes.filter(it => it.startNode)[0];
@@ -51,17 +51,17 @@ const learningPathPersonalizingService = {
 
         while (true) {
             // At every node, calculate all the possible next transitions.
-            let lastSubmission = await getLastRelevantSubmission(currentNode, pathFor);
-            let submitted = lastSubmission === null ? null : JSON.parse(lastSubmission.content);
-            let possibleTransitions = currentNode.transitions
+            const lastSubmission = await getLastRelevantSubmission(currentNode, pathFor);
+            const submitted = lastSubmission === null ? null : JSON.parse(lastSubmission.content);
+            const possibleTransitions = currentNode.transitions
                 .filter(it => transitionPossible(it, submitted));
 
             if (possibleTransitions.length === 0) { // If there are none, the trajectory has ended.
                 return trajectory;
-            } else { // Otherwise, take the first possible transition.
+            }  // Otherwise, take the first possible transition.
                 currentNode = possibleTransitions[0].node;
                 trajectory.push(currentNode);
-            }
+            
         }
     }
 };
diff --git a/backend/src/util/async.ts b/backend/src/util/async.ts
index f37f53a0..874c0b8e 100644
--- a/backend/src/util/async.ts
+++ b/backend/src/util/async.ts
@@ -19,5 +19,5 @@ export async function replaceAsync(str: string, regex: RegExp, replacementFn: (m
     const replacements: string[] = (await Promise.all(promises));
 
     // Second run through matches: Replace them by their previously computed replacements.
-    return str.replace(regex, () => replacements.pop()!!);
+    return str.replace(regex, () => replacements.pop()!);
 }
diff --git a/backend/tests/data/content/attachment-repository.test.ts b/backend/tests/data/content/attachment-repository.test.ts
index 3f573cdb..e6c4e44a 100644
--- a/backend/tests/data/content/attachment-repository.test.ts
+++ b/backend/tests/data/content/attachment-repository.test.ts
@@ -11,10 +11,10 @@ import {LearningObjectIdentifier} from "../../../src/entities/content/learning-o
 const NEWER_TEST_SUFFIX = "nEweR";
 
 function createTestLearningObjects(learningObjectRepo: LearningObjectRepository): {older: LearningObject, newer: LearningObject} {
-    let olderExample = example.createLearningObject();
+    const olderExample = example.createLearningObject();
     learningObjectRepo.save(olderExample);
 
-    let newerExample = example.createLearningObject();
+    const newerExample = example.createLearningObject();
     newerExample.title = "Newer example";
     newerExample.version = 100;
 
@@ -40,7 +40,7 @@ describe("AttachmentRepository", () => {
             .values(example.createAttachment)
             .map(fn => fn(exampleLearningObjects.older));
 
-        for (let attachment of attachmentsOlderLearningObject) {
+        for (const attachment of attachmentsOlderLearningObject) {
             attachmentRepo.save(attachment);
         }
     });
diff --git a/backend/tests/services/learning-objects/database-learning-object-provider.test.ts b/backend/tests/services/learning-objects/database-learning-object-provider.test.ts
index 691b29ba..e3960f64 100644
--- a/backend/tests/services/learning-objects/database-learning-object-provider.test.ts
+++ b/backend/tests/services/learning-objects/database-learning-object-provider.test.ts
@@ -12,8 +12,8 @@ import {FilteredLearningObject} from "../../../src/interfaces/learning-content";
 import {Language} from "../../../src/entities/content/language";
 
 async function initExampleData(): Promise<LearningObject> {
-    let learningObjectRepo = getLearningObjectRepository();
-    let exampleLearningObject = createExampleLearningObjectWithAttachments(example);
+    const learningObjectRepo = getLearningObjectRepository();
+    const exampleLearningObject = createExampleLearningObjectWithAttachments(example);
     await learningObjectRepo.insert(exampleLearningObject);
     return exampleLearningObject;
 }
diff --git a/backend/tests/services/learning-objects/learning-object-service.test.ts b/backend/tests/services/learning-objects/learning-object-service.test.ts
index 970e4675..2a68d797 100644
--- a/backend/tests/services/learning-objects/learning-object-service.test.ts
+++ b/backend/tests/services/learning-objects/learning-object-service.test.ts
@@ -18,7 +18,7 @@ const DWENGO_TEST_LEARNING_OBJECT_ID: LearningObjectIdentifier = {
 
 async function initExampleData(): Promise<LearningObject> {
     const learningObjectRepo = getLearningObjectRepository();
-    let learningObject = learningObjectExample.createLearningObject();
+    const learningObject = learningObjectExample.createLearningObject();
     learningObject.title = TEST_LEARNING_OBJECT_TITLE
     await learningObjectRepo.save(learningObject);
     return learningObject;
diff --git a/backend/tests/services/learning-path/database-learning-path-provider.test.ts b/backend/tests/services/learning-path/database-learning-path-provider.test.ts
index 0d46c1e0..8dd3d07b 100644
--- a/backend/tests/services/learning-path/database-learning-path-provider.test.ts
+++ b/backend/tests/services/learning-path/database-learning-path-provider.test.ts
@@ -14,8 +14,8 @@ import {Language} from "../../../src/entities/content/language";
 async function initExampleData(): Promise<{ learningObject: LearningObject, learningPath: LearningPath }> {
     const learningObjectRepo = getLearningObjectRepository();
     const learningPathRepo = getLearningPathRepository();
-    let learningObject = learningObjectExample.createLearningObject();
-    let learningPath = learningPathExample.createLearningPath();
+    const learningObject = learningObjectExample.createLearningObject();
+    const learningPath = learningPathExample.createLearningPath();
     await learningObjectRepo.save(learningObject);
     await learningPathRepo.save(learningPath);
     return { learningObject, learningPath };
@@ -55,7 +55,7 @@ describe("DatabaseLearningPathProvider", () => {
         it("returns a non-successful response if a non-existing learning path is queried", async () => {
             const result = await databaseLearningPathProvider.fetchLearningPaths(
                 [example.learningPath.hruid],
-                Language.Abkhazian, // wrong language
+                Language.Abkhazian, // Wrong language
                 "the source"
             );
 
diff --git a/backend/tests/services/learning-path/learning-path-service.test.ts b/backend/tests/services/learning-path/learning-path-service.test.ts
index 83db1bef..b64d527a 100644
--- a/backend/tests/services/learning-path/learning-path-service.test.ts
+++ b/backend/tests/services/learning-path/learning-path-service.test.ts
@@ -11,8 +11,8 @@ import learningPathService from "../../../src/services/learning-paths/learning-p
 async function initExampleData(): Promise<{ learningObject: LearningObject, learningPath: LearningPath }> {
     const learningObjectRepo = getLearningObjectRepository();
     const learningPathRepo = getLearningPathRepository();
-    let learningObject = learningObjectExample.createLearningObject();
-    let learningPath = learningPathExample.createLearningPath();
+    const learningObject = learningObjectExample.createLearningObject();
+    const learningPath = learningPathExample.createLearningPath();
     await learningObjectRepo.save(learningObject);
     await learningPathRepo.save(learningPath);
     return { learningObject, learningPath };
@@ -76,7 +76,7 @@ describe("LearningPathService", () => {
                 ).length
             ).toBe(1);
 
-            // but should not only find that one.
+            // But should not only find that one.
             expect(result.length).not.toBeLessThan(2);
         });
         it("should still return results from the Dwengo API even though there are no matches in the database", async () => {
@@ -88,7 +88,7 @@ describe("LearningPathService", () => {
             // Should find something...
             expect(result.length).not.toBe(0);
 
-            // but not the example learning path.
+            // But not the example learning path.
             expect(
                 result.filter(it =>
                     it.hruid === example.learningPath.hruid && it.title === example.learningPath.title
diff --git a/backend/tests/test-assets/learning-objects/create-example-learning-object-with-attachments.ts b/backend/tests/test-assets/learning-objects/create-example-learning-object-with-attachments.ts
index 65d2b62e..c0177fbf 100644
--- a/backend/tests/test-assets/learning-objects/create-example-learning-object-with-attachments.ts
+++ b/backend/tests/test-assets/learning-objects/create-example-learning-object-with-attachments.ts
@@ -2,8 +2,8 @@ import {LearningObjectExample} from "./learning-object-example";
 import {LearningObject} from "../../../src/entities/content/learning-object.entity";
 
 export function createExampleLearningObjectWithAttachments(example: LearningObjectExample): LearningObject {
-    let learningObject = example.createLearningObject();
-    for (let creationFn of Object.values(example.createAttachment)) {
+    const learningObject = example.createLearningObject();
+    for (const creationFn of Object.values(example.createAttachment)) {
         learningObject.attachments.push(creationFn(learningObject));
     }
     return learningObject;
diff --git a/backend/tests/test-assets/learning-objects/pn-werkingnotebooks/pn-werkingnotebooks-example.ts b/backend/tests/test-assets/learning-objects/pn-werkingnotebooks/pn-werkingnotebooks-example.ts
index 09cab0f9..9a7f340c 100644
--- a/backend/tests/test-assets/learning-objects/pn-werkingnotebooks/pn-werkingnotebooks-example.ts
+++ b/backend/tests/test-assets/learning-objects/pn-werkingnotebooks/pn-werkingnotebooks-example.ts
@@ -10,7 +10,7 @@ const ASSETS_PREFIX = "learning-objects/pn-werkingnotebooks/";
 
 const example: LearningObjectExample = {
     createLearningObject: ()=>  {
-        let learningObject = new LearningObject();
+        const learningObject = new LearningObject();
         learningObject.hruid = `${getEnvVar(EnvVars.UserContentPrefix)}pn_werkingnotebooks`;
         learningObject.version = 3;
         learningObject.language = Language.Dutch;
@@ -18,11 +18,11 @@ const example: LearningObjectExample = {
         learningObject.description = "Leren werken met notebooks";
         learningObject.keywords = ["Python", "KIKS", "Wiskunde", "STEM", "AI"]
 
-        let educationalGoal1 = new EducationalGoal();
+        const educationalGoal1 = new EducationalGoal();
         educationalGoal1.source = "Source";
         educationalGoal1.id = "id";
 
-        let educationalGoal2 = new EducationalGoal();
+        const educationalGoal2 = new EducationalGoal();
         educationalGoal2.source = "Source2";
         educationalGoal2.id = "id2";
 
@@ -39,7 +39,7 @@ const example: LearningObjectExample = {
         learningObject.license = "dwengo";
         learningObject.estimatedTime = 10;
 
-        let returnValue = new ReturnValue();
+        const returnValue = new ReturnValue();
         returnValue.callbackUrl = "callback_url_example";
         returnValue.callbackSchema = '{"att": "test", "att2": "test2"}';
 
@@ -51,7 +51,7 @@ const example: LearningObjectExample = {
     },
     createAttachment: {
         dwengoLogo: (learningObject) => {
-            let att = new Attachment();
+            const att = new Attachment();
             att.learningObject = learningObject;
             att.name = "dwengo.png";
             att.mimeType = "image/png";
@@ -59,7 +59,7 @@ const example: LearningObjectExample = {
             return att;
         },
         knop: (learningObject) => {
-            let att = new Attachment();
+            const att = new Attachment();
             att.learningObject = learningObject;
             att.name = "Knop.png";
             att.mimeType = "image/png";
diff --git a/backend/tests/test-assets/learning-paths/learning-path-utils.ts b/backend/tests/test-assets/learning-paths/learning-path-utils.ts
index 68c49412..0a09145f 100644
--- a/backend/tests/test-assets/learning-paths/learning-path-utils.ts
+++ b/backend/tests/test-assets/learning-paths/learning-path-utils.ts
@@ -4,7 +4,7 @@ import {LearningPathNode} from "../../../src/entities/content/learning-path-node
 import {LearningPath} from "../../../src/entities/content/learning-path.entity";
 
 export function createLearningPathTransition(node: LearningPathNode, transitionNumber: number, condition: string | null, to: LearningPathNode) {
-    let trans = new LearningPathTransition();
+    const trans = new LearningPathTransition();
     trans.node = node;
     trans.transitionNumber = transitionNumber;
     trans.condition = condition || "true";
@@ -20,7 +20,7 @@ export function createLearningPathNode(
     language: Language,
     startNode: boolean
 ) {
-    let node = new LearningPathNode();
+    const node = new LearningPathNode();
     node.learningPath = learningPath;
     node.nodeNumber = nodeNumber;
     node.learningObjectHruid = learningObjectHruid;
diff --git a/backend/tests/test-assets/learning-paths/pn-werking-example.ts b/backend/tests/test-assets/learning-paths/pn-werking-example.ts
index a96de552..40a07587 100644
--- a/backend/tests/test-assets/learning-paths/pn-werking-example.ts
+++ b/backend/tests/test-assets/learning-paths/pn-werking-example.ts
@@ -5,7 +5,7 @@ import {createLearningPathNode, createLearningPathTransition} from "./learning-p
 import {LearningPathNode} from "../../../src/entities/content/learning-path-node.entity";
 
 function createNodes(learningPath: LearningPath): LearningPathNode[] {
-    let nodes = [
+    const nodes = [
         createLearningPathNode(learningPath, 0, "u_pn_werkingnotebooks", 3, Language.Dutch, true),
         createLearningPathNode(learningPath, 1, "pn_werkingnotebooks2", 3, Language.Dutch, false),
         createLearningPathNode(learningPath, 2, "pn_werkingnotebooks3", 3, Language.Dutch, false),
diff --git a/backend/tests/test-utils/expectations.ts b/backend/tests/test-utils/expectations.ts
index 19c2408d..b7e9523b 100644
--- a/backend/tests/test-utils/expectations.ts
+++ b/backend/tests/test-utils/expectations.ts
@@ -22,7 +22,7 @@ export function expectToBeCorrectEntity<T extends object>(
     if (!expected.name) {
         expected.name = "expected";
     }
-    for (let property in expected.entity) {
+    for (const property in expected.entity) {
         if (
             property !in IGNORE_PROPERTIES
             && 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.
@@ -34,10 +34,10 @@ export function expectToBeCorrectEntity<T extends object>(
                 });
             }
             if (typeof expected.entity[property] === "boolean") { // Sometimes, booleans get represented by numbers 0 and 1 in the objects actual from the database.
-                if (!!expected.entity[property] !== !!actual.entity[property]) {
+                if (Boolean(expected.entity[property]) !== Boolean(actual.entity[property])) {
                     throw new AssertionError({
                         message: `${property} was ${expected.entity[property]} in ${expected.name},
-                        but ${actual.entity[property]} (${!!expected.entity[property]}) in ${actual.name}`
+                        but ${actual.entity[property]} (${Boolean(expected.entity[property])}) in ${actual.name}`
                     });
                 }
             } else if (typeof expected.entity[property] !== typeof actual.entity[property]) {
@@ -78,7 +78,7 @@ export function expectToBeCorrectFilteredLearningObject(filtered: FilteredLearni
     expect(filtered.key).toEqual(original.hruid);
     expect(filtered.targetAges).toEqual(original.targetAges);
     expect(filtered.title).toEqual(original.title);
-    expect(!!filtered.teacherExclusive).toEqual(original.teacherExclusive) // !!: Workaround: MikroORM with SQLite returns 0 and 1 instead of booleans.
+    expect(Boolean(filtered.teacherExclusive)).toEqual(original.teacherExclusive) // !!: Workaround: MikroORM with SQLite returns 0 and 1 instead of booleans.
     expect(filtered.skosConcepts).toEqual(original.skosConcepts);
     expect(filtered.estimatedTime).toEqual(original.estimatedTime);
     expect(filtered.educationalGoals).toEqual(original.educationalGoals);
@@ -123,21 +123,21 @@ export function expectToBeCorrectLearningPath(
     expect(learningPath.num_nodes).toEqual(expectedEntity.nodes.length);
     expect(learningPath.image || null).toEqual(expectedEntity.image);
 
-    let expectedLearningPathNodes = new Map(
+    const expectedLearningPathNodes = new Map(
         expectedEntity.nodes.map(node => [
             {learningObjectHruid: node.learningObjectHruid, language: node.language, version: node.version},
             {startNode: node.startNode, transitions: node.transitions}
         ])
     );
 
-    for (let node of learningPath.nodes) {
+    for (const node of learningPath.nodes) {
         const nodeKey = {
             learningObjectHruid: node.learningobject_hruid,
             language: node.language,
             version: node.version
         };
         expect(expectedLearningPathNodes.keys()).toContainEqual(nodeKey);
-        let expectedNode = [...expectedLearningPathNodes.entries()]
+        const expectedNode = [...expectedLearningPathNodes.entries()]
             .filter(([key, _]) =>
                 key.learningObjectHruid === nodeKey.learningObjectHruid
                 && key.language === node.language