diff --git a/src/lib/components/QrScanner.svelte b/src/lib/components/QrScanner.svelte
index ca6d3e0..12fa3dd 100644
--- a/src/lib/components/QrScanner.svelte
+++ b/src/lib/components/QrScanner.svelte
@@ -36,11 +36,14 @@
 					scanning = false;
 				},
 				(err) => {
-					notifications.error(err);
+					if ((err as unknown as Error).toString().includes('NotFoundException')) {
+						return;
+					}
+					notifications.error(`error during scanning: ${err}`);
 				}
 			);
 		} catch (err) {
-			notifications.error(`Error starting camera: ${err}`);
+			notifications.error(`error during starting camera: ${err}`);
 			scanning = false;
 		}
 	}
@@ -53,7 +56,15 @@
 			const result = await scanner.scanFile(file, true);
 			onScan(result);
 		} catch (err) {
-			notifications.error(`Error scanning file: ${err}`);
+			if ((err as unknown as Error).toString().includes('NotFoundException')) {
+				notifications.error(
+					'Unable to find QR code in the image. Please ensure the image is clear and contains a valid QR code.'
+				);
+			} else {
+				notifications.error(`error during scanning file: ${err}`);
+			}
+		} finally {
+			fileInput.value = '';
 		}
 	}
 </script>
diff --git a/tests/firebase.test.ts b/tests/firebase.test.ts
new file mode 100644
index 0000000..368c913
--- /dev/null
+++ b/tests/firebase.test.ts
@@ -0,0 +1,166 @@
+import type { CollectionReference, DocumentReference } from 'firebase-admin/firestore';
+import { beforeEach, describe, expect, it, vi } from 'vitest';
+import {
+	adminDb,
+	checkRemoveParticipantPermission,
+	getGroupsData,
+	getSessionData
+} from '../src/lib/server/firebase';
+
+// Mock Firestore
+vi.mock('firebase-admin/firestore', () => ({
+	getFirestore: vi.fn(() => ({
+		collection: vi.fn(),
+		doc: vi.fn()
+	})),
+	Timestamp: {
+		now: vi.fn(() => ({ toMillis: () => 1234567890000 }))
+	}
+}));
+
+describe('Firebase Server Functions', () => {
+	beforeEach(() => {
+		vi.clearAllMocks();
+	});
+
+	describe('getGroupsData', () => {
+		it('應該正確返回群組資料', async () => {
+			const mockGroups = {
+				empty: false,
+				docs: [
+					{
+						data: () => ({
+							number: 1,
+							participants: ['user1', 'user2'],
+							concept: null
+						})
+					},
+					{
+						data: () => ({
+							number: 2,
+							participants: ['user3', 'user4'],
+							concept: null
+						})
+					}
+				]
+			};
+
+			const groupsRef = {
+				get: vi.fn().mockResolvedValue(mockGroups)
+			} as unknown as CollectionReference;
+
+			const result = await getGroupsData(groupsRef);
+			expect(result).toHaveLength(2);
+			expect(result[0].number).toBe(1);
+			expect(result[1].participants).toContain('user3');
+		});
+
+		it('當沒有找到群組時應該拋出404錯誤', async () => {
+			const groupsRef = {
+				get: vi.fn().mockResolvedValue({ empty: true })
+			} as unknown as CollectionReference;
+
+			await expect(getGroupsData(groupsRef)).rejects.toThrow('Groups not found');
+		});
+	});
+
+	describe('getSessionData', () => {
+		it('應該正確返回會話資料', async () => {
+			const mockSession = {
+				exists: true,
+				data: () => ({
+					title: 'Test Session',
+					host: 'user1',
+					status: 'preparing'
+				})
+			};
+
+			const sessionRef = {
+				get: vi.fn().mockResolvedValue(mockSession)
+			} as unknown as DocumentReference;
+
+			const result = await getSessionData(sessionRef);
+			expect(result.title).toBe('Test Session');
+			expect(result.host).toBe('user1');
+		});
+
+		it('當沒有找到會話時應該拋出404錯誤', async () => {
+			const sessionRef = {
+				get: vi.fn().mockResolvedValue({ exists: false })
+			} as unknown as DocumentReference;
+
+			await expect(getSessionData(sessionRef)).rejects.toThrow('Session not found');
+		});
+	});
+
+	describe('checkRemoveParticipantPermission', () => {
+		it('當使用者是主持人時應該返回true', async () => {
+			const mockSession = {
+				exists: true,
+				data: () => ({
+					host: 'host123',
+					status: 'preparing'
+				})
+			};
+
+			vi.spyOn(adminDb, 'collection').mockReturnValue({
+				doc: vi.fn().mockReturnValue({
+					get: vi.fn().mockResolvedValue(mockSession)
+				})
+			} as unknown as CollectionReference);
+
+			const result = await checkRemoveParticipantPermission(
+				'session123',
+				'host123',
+				'participant123'
+			);
+			expect(result).toBe(true);
+		});
+
+		it('當使用者是被移除的參與者時應該返回true', async () => {
+			const mockSession = {
+				exists: true,
+				data: () => ({
+					host: 'host123',
+					status: 'preparing'
+				})
+			};
+
+			vi.spyOn(adminDb, 'collection').mockReturnValue({
+				doc: vi.fn().mockReturnValue({
+					get: vi.fn().mockResolvedValue(mockSession)
+				})
+			} as unknown as CollectionReference);
+
+			const result = await checkRemoveParticipantPermission(
+				'session123',
+				'participant123',
+				'participant123'
+			);
+			expect(result).toBe(true);
+		});
+
+		it('當使用者既不是主持人也不是被移除的參與者時應該返回false', async () => {
+			const mockSession = {
+				exists: true,
+				data: () => ({
+					host: 'host123',
+					status: 'preparing'
+				})
+			};
+
+			vi.spyOn(adminDb, 'collection').mockReturnValue({
+				doc: vi.fn().mockReturnValue({
+					get: vi.fn().mockResolvedValue(mockSession)
+				})
+			} as unknown as CollectionReference);
+
+			const result = await checkRemoveParticipantPermission(
+				'session123',
+				'otherUser123',
+				'participant123'
+			);
+			expect(result).toBe(false);
+		});
+	});
+});
diff --git a/tests/getUser.test.ts b/tests/getUser.test.ts
new file mode 100644
index 0000000..bddd7e8
--- /dev/null
+++ b/tests/getUser.test.ts
@@ -0,0 +1,79 @@
+import type { DocumentReference, DocumentSnapshot } from 'firebase/firestore';
+import { doc, getDoc } from 'firebase/firestore';
+import type { Mock } from 'vitest';
+import { beforeEach, describe, expect, it, vi } from 'vitest';
+import { getUser } from '../src/lib/utils/getUser';
+
+// Mock Firebase
+vi.mock('firebase/firestore', () => ({
+	doc: vi.fn(),
+	getDoc: vi.fn()
+}));
+
+vi.mock('$lib/firebase', () => ({
+	db: {}
+}));
+
+describe('getUser', () => {
+	beforeEach(() => {
+		vi.clearAllMocks();
+	});
+
+	it('應該正確返回使用者資料', async () => {
+		const mockUserData = {
+			uid: 'test122',
+			displayName: 'Test User',
+			title: 'Developer',
+			bio: 'Hello World'
+		};
+
+		(doc as unknown as Mock).mockReturnValue({} as DocumentReference);
+		(getDoc as unknown as Mock).mockResolvedValue({
+			exists: () => true,
+			data: () => mockUserData
+		} as unknown as DocumentSnapshot);
+
+		const user = await getUser('test123');
+		expect(user).toEqual(mockUserData);
+	});
+
+	it('當使用者不存在時應該返回預設資料', async () => {
+		const uid = 'nonexistent123';
+		(doc as unknown as Mock).mockReturnValue({} as DocumentReference);
+		(getDoc as unknown as Mock).mockResolvedValue({
+			exists: () => false,
+			data: () => null
+		} as unknown as DocumentSnapshot);
+
+		const user = await getUser(uid);
+		expect(user).toEqual({
+			uid,
+			displayName: uid,
+			title: null,
+			bio: null
+		});
+	});
+
+	it('應該快取使用者資料', async () => {
+		const mockUserData = {
+			uid: 'test122',
+			displayName: 'Test User',
+			title: 'Developer',
+			bio: 'Hello World'
+		};
+
+		(doc as unknown as Mock).mockReturnValue({} as DocumentReference);
+		(getDoc as unknown as Mock).mockResolvedValue({
+			exists: () => true,
+			data: () => mockUserData
+		} as unknown as DocumentSnapshot);
+
+		// 第一次呼叫
+		await getUser('test122');
+		// 第二次呼叫
+		await getUser('test122');
+
+		// 應該只呼叫一次 getDoc
+		expect(getDoc).toHaveBeenCalledTimes(1);
+	});
+});