test: UserInfoProvider 단위테스트 추가

Author: BHyeonKim

src/app/provider/UserInfoProvider.test.tsx

@@ -0,0 +1,56 @@
+import { act, renderHook } from '@testing-library/react';
+import { describe, expect, it, vi } from 'vitest';
+import UserIdProvider, { useUserId } from './UserInfoProvider';
+
+vi.mock('window', () => {
+	const store = new Map();
+	return {
+		localStorage: {
+			getItem: vi.fn((key) => store.get(key)),
+			setItem: vi.fn((key, value) => store.set(key, value)),
+			removeItem: vi.fn((key) => store.delete(key)),
+		},
+	};
+});
+
+const MOCK_USERID = 4;
+
+describe('UserInfoProvider 테스트', () => {
+	it('useUserId hook은 UserInfoProvider 외부에서 사용하면 에러를 던진다.', () => {
+		expect(() => renderHook(() => useUserId())).toThrowError();
+	});
+
+	it('초기 상태에서는 userId가 null이다.', () => {
+		const { result } = renderHook(useUserId, {
+			wrapper: ({ children }) => <UserIdProvider>{children}</UserIdProvider>,
+		});
+
+		expect(result.current.userId).toBe(null);
+	});
+
+	it('초기 마운트 시 로컬스토리지에서 userId를 불러온다.', () => {
+		// Pre-populate localStorage
+		window.localStorage.setItem('userId', MOCK_USERID.toString());
+
+		const { result } = renderHook(useUserId, {
+			wrapper: ({ children }) => <UserIdProvider>{children}</UserIdProvider>,
+		});
+
+		expect(result.current.userId).toBe(MOCK_USERID);
+		expect(window.localStorage.getItem).toHaveBeenCalledWith('userId');
+	});
+
+	it('setUserId를 호출하면 userId 상태가 업데이트된다.', () => {
+		const { result } = renderHook(useUserId, {
+			wrapper: ({ children }) => <UserIdProvider>{children}</UserIdProvider>,
+		});
+
+		expect(result.current.userId).toBe(null);
+
+		act(() => {
+			result.current.setUserId(MOCK_USERID);
+		});
+
+		expect(result.current.userId).toBe(MOCK_USERID);
+	});
+});