♻️ Improve tests (#1924)

Author: KATO-Hiro

src/test/lib/stores/active_contest_type.svelte.test.ts

@@ -14,13 +14,16 @@ describe('ActiveContestTypeStore', () => {
   let store: ActiveContestTypeStore;
 
   const mockLocalStorage: Storage = {
-    getItem: vi.fn(),
-    setItem: vi.fn(),
+    getItem: vi.fn((key) => mockStorage[key] || null),
+    setItem: vi.fn((key, value) => {
+      mockStorage[key] = value;
+    }),
     removeItem: vi.fn(),
     clear: vi.fn(),
     length: 0,
     key: vi.fn(),
   };
+  const mockStorage: Record<string, string> = {};
 
   beforeEach(() => {
     vi.clearAllMocks();
@@ -96,11 +99,16 @@ describe('ActiveContestTypeStore', () => {
 
 describe('Active contest type store in SSR', () => {
   beforeEach(() => {
+    vi.restoreAllMocks();
     vi.mock('$app/environment', () => ({
       browser: false,
     }));
   });
 
+  afterEach(() => {
+    vi.restoreAllMocks();
+  });
+
   test('handles SSR gracefully', () => {
     expect(activeContestTypeStore.get()).toBe('abcLatest20Rounds');
   });

src/test/lib/stores/active_problem_list_tab.svelte.test.ts

@@ -13,13 +13,16 @@ describe('ActiveProblemListTabStore', () => {
   let store: ActiveProblemListTabStore;
 
   const mockLocalStorage: Storage = {
-    getItem: vi.fn(),
-    setItem: vi.fn(),
+    getItem: vi.fn((key) => mockStorage[key] || null),
+    setItem: vi.fn((key, value) => {
+      mockStorage[key] = value;
+    }),
     removeItem: vi.fn(),
     clear: vi.fn(),
     length: 0,
     key: vi.fn(),
   };
+  const mockStorage: Record<string, string> = {};
 
   beforeEach(() => {
     vi.clearAllMocks();
@@ -87,11 +90,16 @@ describe('ActiveProblemListTabStore', () => {
 
 describe('Active problem list tab store in SSR', () => {
   beforeEach(() => {
+    vi.restoreAllMocks();
     vi.mock('$app/environment', () => ({
       browser: false,
     }));
   });
 
+  afterEach(() => {
+    vi.restoreAllMocks();
+  });
+
   test('handles SSR gracefully', () => {
     expect(activeProblemListTabStore.get()).toBe('contestTable');
   });