diff --git a/frontend/src/hooks/useLocalStorage.test.ts b/frontend/src/hooks/useLocalStorage.test.ts
new file mode 100644
index 000000000..a4332e21f
--- /dev/null
+++ b/frontend/src/hooks/useLocalStorage.test.ts
@@ -0,0 +1,116 @@
+import { act, renderHook } from '@testing-library/react';
+import { afterEach, describe, expect, test } from 'vitest';
+
+import { LEVEL_NAMES } from '@src/models/level';
+
+import useLocalStorage from './useLocalStorage';
+
+const newUserKey = 'isNewUser';
+const currentLevelKey = 'currentLevel';
+const completedLevelsKey = 'numCompletedLevels';
+
+describe('useLocalStorage hook', () => {
+	afterEach(() => {
+		localStorage.clear();
+	});
+
+	test.each([true, false])(
+		`Reads ${newUserKey} from localStorage on init`,
+		(isNewUser) => {
+			localStorage.setItem(newUserKey, `${isNewUser}`);
+
+			const { result } = renderHook(useLocalStorage);
+			expect(result.current.isNewUser).toBe(isNewUser);
+		}
+	);
+
+	test(`Default to ${newUserKey}=true when unset`, () => {
+		const { result } = renderHook(useLocalStorage);
+		expect(result.current.isNewUser).toBe(true);
+	});
+
+	test(`Reads ${currentLevelKey} from localStorage on init, if not new user`, () => {
+		localStorage.setItem(newUserKey, 'false');
+		localStorage.setItem(currentLevelKey, LEVEL_NAMES.LEVEL_3.toString());
+
+		const { result } = renderHook(useLocalStorage);
+		expect(result.current.currentLevel).toBe(LEVEL_NAMES.LEVEL_3);
+	});
+
+	test(`Ignores ${currentLevelKey} in localStorage on init, if new user`, () => {
+		localStorage.setItem(newUserKey, 'true');
+		localStorage.setItem(currentLevelKey, LEVEL_NAMES.LEVEL_3.toString());
+
+		const { result } = renderHook(useLocalStorage);
+		expect(result.current.currentLevel).toBe(LEVEL_NAMES.LEVEL_1);
+	});
+
+	test(`Reads ${completedLevelsKey} from localStorage on init, if not new user`, () => {
+		localStorage.setItem(newUserKey, 'false');
+		localStorage.setItem(completedLevelsKey, '2');
+
+		const { result } = renderHook(useLocalStorage);
+		expect(result.current.numCompletedLevels).toBe(2);
+	});
+
+	test(`Ignores ${completedLevelsKey} in localStorage on init, if new user`, () => {
+		localStorage.setItem(newUserKey, 'true');
+		localStorage.setItem(completedLevelsKey, '2');
+
+		const { result } = renderHook(useLocalStorage);
+		expect(result.current.currentLevel).toBe(0);
+	});
+
+	test(`Persists ${newUserKey} in storage when set`, () => {
+		const { result } = renderHook(useLocalStorage);
+		expect(result.current.isNewUser).toBe(true);
+
+		act(() => {
+			result.current.setIsNewUser(false);
+		});
+
+		expect(result.current.isNewUser).toBe(false);
+		expect(localStorage.getItem(newUserKey)).toEqual('false');
+	});
+
+	test(`Persists ${currentLevelKey} in storage when set`, () => {
+		const { result } = renderHook(useLocalStorage);
+		expect(result.current.currentLevel).toBe(LEVEL_NAMES.LEVEL_1);
+
+		act(() => {
+			result.current.setCurrentLevel(LEVEL_NAMES.LEVEL_3);
+		});
+
+		expect(result.current.currentLevel).toBe(LEVEL_NAMES.LEVEL_3);
+		expect(localStorage.getItem(currentLevelKey)).toEqual(
+			`${LEVEL_NAMES.LEVEL_3}`
+		);
+	});
+
+	test(`Persists ${completedLevelsKey} in storage when set`, () => {
+		const { result } = renderHook(useLocalStorage);
+		expect(result.current.numCompletedLevels).toBe(0);
+
+		act(() => {
+			result.current.setCompletedLevels(2);
+		});
+
+		expect(result.current.numCompletedLevels).toBe(2);
+		expect(localStorage.getItem(completedLevelsKey)).toEqual('2');
+	});
+
+	test(`${completedLevelsKey} is unchanged when setting it lower than current`, () => {
+		localStorage.setItem(newUserKey, 'false');
+		localStorage.setItem(completedLevelsKey, '3');
+
+		const { result } = renderHook(useLocalStorage);
+		expect(result.current.numCompletedLevels).toBe(3);
+
+		act(() => {
+			result.current.setCompletedLevels(2);
+		});
+
+		expect(result.current.numCompletedLevels).toBe(3);
+		expect(localStorage.getItem(completedLevelsKey)).toEqual('3');
+	});
+});
diff --git a/frontend/src/hooks/useLocalStorage.ts b/frontend/src/hooks/useLocalStorage.ts
index 9b6939a1e..80cd32768 100644
--- a/frontend/src/hooks/useLocalStorage.ts
+++ b/frontend/src/hooks/useLocalStorage.ts
@@ -4,6 +4,7 @@ import { LEVEL_NAMES } from '@src/models/level';
 
 export default function useLocalStorage() {
 	const [isNewUser, setNewUser] = useState(loadIsNewUser);
+
 	const setIsNewUser = useCallback((isNew: boolean) => {
 		setNewUser(isNew);
 		localStorage.setItem('isNewUser', isNew.toString());
@@ -12,6 +13,7 @@ export default function useLocalStorage() {
 	const [currentLevel, setLevel] = useState<LEVEL_NAMES>(
 		loadCurrentLevel(isNewUser)
 	);
+
 	const setCurrentLevel = useCallback((level: LEVEL_NAMES) => {
 		setLevel(level);
 		localStorage.setItem('currentLevel', level.toString());
@@ -20,10 +22,15 @@ export default function useLocalStorage() {
 	const [numCompletedLevels, setNumCompletedLevels] = useState(
 		loadNumCompletedLevels(isNewUser)
 	);
+
 	const setCompletedLevels = useCallback((levels: number) => {
-		setNumCompletedLevels((prev) => Math.max(prev, levels));
-		localStorage.setItem('numCompletedLevels', levels.toString());
+		setNumCompletedLevels((prev) => {
+			const completed = Math.max(prev, levels);
+			localStorage.setItem('numCompletedLevels', `${completed}`);
+			return completed;
+		});
 	}, []);
+
 	const resetCompletedLevels = useCallback(() => {
 		setNumCompletedLevels(0);
 		localStorage.setItem('numCompletedLevels', '0');
@@ -47,11 +54,16 @@ function loadIsNewUser() {
 
 function loadCurrentLevel(isNewUser: boolean) {
 	const levelInStorage = localStorage.getItem('currentLevel');
-	const level = (levelInStorage && !isNewUser)
-		? parseInt(levelInStorage)
-		: LEVEL_NAMES.LEVEL_1
+	const level =
+		levelInStorage && !isNewUser
+			? parseInt(levelInStorage)
+			: LEVEL_NAMES.LEVEL_1;
 
-	if (Number.isNaN(level) || level < LEVEL_NAMES.LEVEL_1 || level > LEVEL_NAMES.SANDBOX) {
+	if (
+		Number.isNaN(level) ||
+		level < LEVEL_NAMES.LEVEL_1 ||
+		level > LEVEL_NAMES.SANDBOX
+	) {
 		console.error(
 			`Invalid level ${level} in local storage, defaulting to level 1`
 		);