diff --git a/backend/CONSOLE_DEBUG_COMMANDS.md b/backend/CONSOLE_DEBUG_COMMANDS.md
new file mode 100644
index 00000000..9b685c3c
--- /dev/null
+++ b/backend/CONSOLE_DEBUG_COMMANDS.md
@@ -0,0 +1,207 @@
+# 🔍 Команды для отладки календаря через консоль браузера
+
+Откройте консоль браузера (F12 → Console) и выполните эти команды:
+
+## 1️⃣ Проверить наличие интеграции
+
+```javascript
+// Должно вернуть объект, а не undefined
+window.calendarIntegration
+```
+
+**Ожидаемый результат:**
+```javascript
+{
+  fetchEventsForVisibleCalendars: ƒ,
+  getVisibleCalendarIds: ƒ,
+  getCalendars: ƒ,
+  setVisibleCalendars: ƒ,
+  refresh: ƒ,
+  instances: {manager: {...}, modal: {...}, widget: {...}}
+}
+```
+
+**Если undefined** → интеграция не инициализировалась!
+
+---
+
+## 2️⃣ Проверить виджет календаря
+
+```javascript
+window.calendarWidget
+```
+
+**Должен вернуть объект FullCalendar**
+
+---
+
+## 3️⃣ Проверить список календарей
+
+```javascript
+// Если интеграция работает:
+window.calendarIntegration.getCalendars()
+
+// Должно вернуть массив календарей:
+// [{id: 1, title: "Personal", color: "#0d6efd", ...}, ...]
+```
+
+---
+
+## 4️⃣ Проверить видимые календари
+
+```javascript
+window.calendarIntegration.getVisibleCalendarIds()
+
+// Должно вернуть массив ID: [1, 2, 3]
+```
+
+---
+
+## 5️⃣ Вручную загрузить события
+
+```javascript
+// Попробовать загрузить события для видимых календарей
+const start = new Date('2026-02-01');
+const end = new Date('2026-02-28');
+
+window.calendarIntegration.fetchEventsForVisibleCalendars(start, end)
+  .then(events => {
+    console.log('✅ Events loaded:', events.length);
+    console.table(events);
+  })
+  .catch(err => {
+    console.error('❌ Error:', err);
+  });
+```
+
+---
+
+## 6️⃣ Проверить, загружен ли скрипт интеграции
+
+```javascript
+// Проверить, есть ли в DOM скрипт
+document.querySelector('script[src*="calendarWidgetIntegration"]')
+
+// Должен вернуть <script> элемент, если файл подключен
+```
+
+---
+
+## 7️⃣ Вручную инициализировать интеграцию
+
+Если интеграция не загрузилась автоматически, попробуйте вручную:
+
+```javascript
+// 1. Импортировать модуль (если ES6 modules работают)
+import('/static/js/components/calendarWidgetIntegration.js')
+  .then(module => {
+    const { integrateCalendarManager } = module;
+    const integration = integrateCalendarManager(window.calendarWidget);
+    window.calendarIntegration = integration;
+    console.log('✅ Integration manually initialized');
+  })
+  .catch(err => console.error('❌ Import failed:', err));
+```
+
+---
+
+## 8️⃣ Перезагрузить события календаря
+
+```javascript
+// После того как интеграция инициализирована
+if (window.calendarWidget && window.calendarWidget.refetchEvents) {
+  window.calendarWidget.refetchEvents();
+  console.log('🔄 Events refetched');
+}
+```
+
+---
+
+## 9️⃣ Проверить контейнер списка календарей
+
+```javascript
+// Проверить, существует ли контейнер
+const container = document.getElementById('calendarListContainer');
+console.log('Container exists:', !!container);
+console.log('Container HTML:', container?.innerHTML.substring(0, 200));
+```
+
+---
+
+## 🔟 Проверить модальное окно
+
+```javascript
+// Проверить, есть ли модальное окно
+const modal = document.getElementById('calendarManageModal');
+console.log('Modal exists:', !!modal);
+
+// Попробовать открыть модальное окно
+if (window.calendarIntegration?.instances?.modal) {
+  window.calendarIntegration.instances.modal.openForCreate();
+}
+```
+
+---
+
+## 🐛 Диагностика проблемы
+
+Выполните все команды по порядку и скопируйте результаты. Это поможет понять, на каком этапе происходит сбой:
+
+```javascript
+console.log('=== Calendar Integration Debug ===');
+console.log('1. calendarIntegration:', typeof window.calendarIntegration);
+console.log('2. calendarWidget:', typeof window.calendarWidget);
+console.log('3. Container:', !!document.getElementById('calendarListContainer'));
+console.log('4. Modal:', !!document.getElementById('calendarManageModal'));
+console.log('5. Create button:', !!document.querySelector('[data-action="create-calendar"]'));
+console.log('=================================');
+```
+
+---
+
+## 🔧 Если интеграция undefined
+
+Проверьте, загружается ли файл `calendar_scripts.html`:
+
+```javascript
+// Найти все script теги с calendar
+Array.from(document.querySelectorAll('script[type="module"]'))
+  .filter(s => s.textContent.includes('calendar'))
+  .forEach(s => console.log('Found:', s.textContent.substring(0, 100)));
+```
+
+---
+
+## 📊 Полный отчёт о состоянии
+
+Скопируйте и выполните весь блок:
+
+```javascript
+(function debugCalendar() {
+  const report = {
+    integration: typeof window.calendarIntegration,
+    widget: typeof window.calendarWidget,
+    container: !!document.getElementById('calendarListContainer'),
+    modal: !!document.getElementById('calendarManageModal'),
+    createButton: !!document.querySelector('[data-action="create-calendar"]'),
+    scripts: Array.from(document.querySelectorAll('script[type="module"]')).length,
+    errors: []
+  };
+  
+  if (window.calendarIntegration) {
+    try {
+      report.calendars = window.calendarIntegration.getCalendars().length;
+      report.visibleIds = window.calendarIntegration.getVisibleCalendarIds();
+    } catch (e) {
+      report.errors.push('Error accessing integration: ' + e.message);
+    }
+  }
+  
+  console.table(report);
+  return report;
+})();
+```
+
+---
+
+Выполните команды и покажите результаты! 🔍
diff --git a/backend/FIX_INTEGRATION.md b/backend/FIX_INTEGRATION.md
new file mode 100644
index 00000000..42fb0062
--- /dev/null
+++ b/backend/FIX_INTEGRATION.md
@@ -0,0 +1,60 @@
+# 🔧 Исправление проблемы инициализации calendar integration
+
+## Проблема
+`window.calendarIntegration` = undefined, но скрипт подключён.
+
+## Быстрое решение - выполните в консоли:
+
+```javascript
+// Проверка наличия скрипта
+const scripts = Array.from(document.querySelectorAll('script[type="module"]'));
+console.log('Module scripts found:', scripts.length);
+scripts.forEach((s, i) => {
+  if (s.textContent.includes('calendar')) {
+    console.log(`Script ${i}:`, s.textContent.substring(0, 200));
+  }
+});
+```
+
+## Если скрипт найден, но не работает - вручную загрузите:
+
+```javascript
+(async function manualInit() {
+  try {
+    console.log('🔄 Manually loading calendar integration...');
+    
+    // Импорт модуля
+    const module = await import('/static/js/components/calendarWidgetIntegration.js');
+    console.log('✅ Module loaded:', module);
+    
+    // Инициализация
+    const { integrateCalendarManager } = module;
+    const integration = integrateCalendarManager(window.calendarWidget);
+    
+    if (integration) {
+      window.calendarIntegration = integration;
+      console.log('✅ Integration initialized successfully!');
+      console.log('Calendars:', integration.getCalendars().length);
+      console.log('Visible:', integration.getVisibleCalendarIds());
+      
+      // Перезагрузить события
+      if (window.calendarWidget.refetchEvents) {
+        window.calendarWidget.refetchEvents();
+        console.log('🔄 Events refetched with new integration');
+      }
+    }
+  } catch (error) {
+    console.error('❌ Manual init failed:', error);
+  }
+})();
+```
+
+## После выполнения проверьте:
+
+```javascript
+// Должно вернуть объект, а не undefined
+window.calendarIntegration
+
+// Должно показать логи с новой системой
+window.calendarWidget.refetchEvents()
+```
diff --git a/backend/static/js/components/calendarWidgetIntegration.js b/backend/static/js/components/calendarWidgetIntegration.js
index 20ae7202..5ae2cf31 100644
--- a/backend/static/js/components/calendarWidgetIntegration.js
+++ b/backend/static/js/components/calendarWidgetIntegration.js
@@ -41,19 +41,22 @@ export function integrateCalendarManager(calendarWidgetInstance, options = {}) {
       range: `${startStr} - ${endStr}`
     });
 
-    // Если нет календарей в новой системе, используем legacy режим
+    // Если нет календарей в новой системе, используем legacy режим (показываем ВСЕ события)
     if (calendars.length === 0) {
-      console.log('[CalendarIntegration] Using legacy mode (no calendars configured)');
+      console.log('[CalendarIntegration] No calendars configured, using legacy mode (showing all events)');
       return await getCalendarEvents({
         start: startStr,
         end: endStr
       });
     }
 
-    // Если ни один календарь не выбран, возвращаем пустой массив
+    // Если ни один календарь не выбран, ТОЖЕ показываем все события (legacy режим)
     if (visibleCalendarIds.length === 0) {
-      console.log('[CalendarIntegration] No calendars selected, returning empty array');
-      return [];
+      console.log('[CalendarIntegration] No calendars selected, falling back to legacy mode');
+      return await getCalendarEvents({
+        start: startStr,
+        end: endStr
+      });
     }
 
     // Загружаем события для каждого видимого календаря
diff --git a/backend/templates/includes/components/calendar_scripts.html b/backend/templates/includes/components/calendar_scripts.html
index 7354c681..b6bdbc53 100644
--- a/backend/templates/includes/components/calendar_scripts.html
+++ b/backend/templates/includes/components/calendar_scripts.html
@@ -5,18 +5,35 @@
   import { initCalendarWidget } from '{% static "js/components/calendarWidget.js" %}';
   import { integrateCalendarManager } from '{% static "js/components/calendarWidgetIntegration.js" %}';
   
-  // Инициализация базового виджета календаря
-  const widget = initCalendarWidget();
-  
-  if (widget) {
-    window.calendarWidget = widget;
+  // Функция инициализации интеграции
+  function initializeIntegration() {
+    // Проверяем, есть ли уже виджет
+    const widget = window.calendarWidget || initCalendarWidget();
     
-    // Интеграция с менеджером календарей
-    const integration = integrateCalendarManager(widget);
-    if (integration) {
-      window.calendarIntegration = integration;
-      console.log('[Calendar] Integration initialized with multiple calendars support');
+    if (widget) {
+      window.calendarWidget = widget;
+      
+      // Интеграция с менеджером календарей
+      const integration = integrateCalendarManager(widget);
+      if (integration) {
+        window.calendarIntegration = integration;
+        console.log('[Calendar] Integration initialized with multiple calendars support');
+      } else {
+        console.warn('[Calendar] Integration failed to initialize');
+      }
+    } else {
+      console.warn('[Calendar] Widget not found, retrying in 500ms...');
+      setTimeout(initializeIntegration, 500);
     }
   }
+  
+  // Инициализация после загрузки DOM
+  if (document.readyState === 'loading') {
+    document.addEventListener('DOMContentLoaded', initializeIntegration);
+  } else {
+    // DOM уже загружен
+    initializeIntegration();
+  }
 </script>
 
+
diff --git a/backend/test_calendar_frontend.html b/backend/test_calendar_frontend.html
new file mode 100644
index 00000000..d57483ff
--- /dev/null
+++ b/backend/test_calendar_frontend.html
@@ -0,0 +1,758 @@
+<!DOCTYPE html>
+<html lang="ru">
+<head>
+  <meta charset="UTF-8">
+  <meta name="viewport" content="width=device-width, initial-scale=1.0">
+  <title>Calendar Frontend Test</title>
+  
+  <!-- Bootstrap CSS (offline fallback) -->
+  <style>
+    @import url('https://cdn.jsdelivr.net/npm/bootstrap@5.3.0/dist/css/bootstrap.min.css');
+    @import url('https://cdn.jsdelivr.net/npm/bootstrap-icons@1.11.0/font/bootstrap-icons.css');
+  </style>
+  
+  <!-- Inline styles as fallback -->
+  <style>
+    body {
+      padding: 20px;
+      background: #f8f9fa;
+    }
+    
+    .test-section {
+      background: white;
+      border-radius: 8px;
+      padding: 20px;
+      margin-bottom: 20px;
+      box-shadow: 0 2px 4px rgba(0,0,0,0.1);
+    }
+    
+    .test-header {
+      display: flex;
+      justify-content: space-between;
+      align-items: center;
+      margin-bottom: 15px;
+      padding-bottom: 15px;
+      border-bottom: 2px solid #e9ecef;
+    }
+    
+    .status-badge {
+      padding: 5px 10px;
+      border-radius: 4px;
+      font-size: 12px;
+      font-weight: bold;
+    }
+    
+    .status-pending { background: #ffc107; color: #000; }
+    .status-success { background: #28a745; color: #fff; }
+    .status-error { background: #dc3545; color: #fff; }
+    
+    .log-console {
+      background: #2d2d2d;
+      color: #f8f8f2;
+      padding: 15px;
+      border-radius: 4px;
+      font-family: 'Courier New', monospace;
+      font-size: 13px;
+      max-height: 400px;
+      overflow-y: auto;
+      margin-top: 15px;
+    }
+    
+    .log-entry {
+      margin: 3px 0;
+      padding: 2px 0;
+    }
+    
+    .log-info { color: #66d9ef; }
+    .log-success { color: #a6e22e; }
+    .log-error { color: #f92672; }
+    .log-warn { color: #e6db74; }
+    
+    #calendarContainer {
+      min-height: 600px;
+      background: white;
+      padding: 20px;
+      border-radius: 8px;
+    }
+    
+    .calendar-list-container {
+      max-height: 400px;
+      overflow-y: auto;
+      border: 1px solid #dee2e6;
+      border-radius: 4px;
+      padding: 10px;
+      background: white;
+    }
+    
+    .calendar-list-item {
+      padding: 10px;
+      margin-bottom: 8px;
+      border: 1px solid #e9ecef;
+      border-radius: 4px;
+      display: flex;
+      align-items: center;
+      gap: 10px;
+      transition: all 0.2s;
+    }
+    
+    .calendar-list-item:hover {
+      background: #f8f9fa;
+      border-color: #0d6efd;
+    }
+    
+    .calendar-color-indicator {
+      width: 12px;
+      height: 12px;
+      border-radius: 50%;
+      border: 2px solid rgba(0,0,0,0.1);
+      flex-shrink: 0;
+    }
+    
+    .calendar-list-item-info {
+      flex: 1;
+      min-width: 0;
+    }
+    
+    .calendar-list-item-title {
+      font-weight: 600;
+      font-size: 14px;
+      margin: 0;
+      white-space: nowrap;
+      overflow: hidden;
+      text-overflow: ellipsis;
+    }
+    
+    .calendar-list-item-meta {
+      font-size: 12px;
+      color: #6c757d;
+      margin: 2px 0 0 0;
+    }
+    
+    .calendar-list-item-actions {
+      display: flex;
+      gap: 5px;
+      flex-shrink: 0;
+    }
+  </style>
+</head>
+<body>
+  <div class="container-fluid">
+    <h1 class="mb-4">🧪 Calendar Frontend Test Suite</h1>
+    
+    <!-- Test Controls -->
+    <div class="test-section">
+      <div class="test-header">
+        <h3>🎮 Test Controls</h3>
+        <div>
+          <button id="runAllTests" class="btn btn-primary">
+            <i class="bi-play-fill"></i> Run All Tests
+          </button>
+          <button id="clearLogs" class="btn btn-secondary">
+            <i class="bi-trash"></i> Clear Logs
+          </button>
+        </div>
+      </div>
+      
+      <div class="row g-3">
+        <div class="col-md-4">
+          <button id="testApiWrapper" class="btn btn-outline-primary w-100">
+            Test 1: API Wrapper
+          </button>
+        </div>
+        <div class="col-md-4">
+          <button id="testCalendarManager" class="btn btn-outline-primary w-100">
+            Test 2: Calendar Manager
+          </button>
+        </div>
+        <div class="col-md-4">
+          <button id="testModalComponent" class="btn btn-outline-primary w-100">
+            Test 3: Modal Component
+          </button>
+        </div>
+        <div class="col-md-4">
+          <button id="testWidgetIntegration" class="btn btn-outline-primary w-100">
+            Test 4: Widget Integration
+          </button>
+        </div>
+        <div class="col-md-4">
+          <button id="testEventFiltering" class="btn btn-outline-primary w-100">
+            Test 5: Event Filtering
+          </button>
+        </div>
+        <div class="col-md-4">
+          <button id="testUserInteractions" class="btn btn-outline-primary w-100">
+            Test 6: User Interactions
+          </button>
+        </div>
+      </div>
+    </div>
+    
+    <!-- Test Results -->
+    <div class="test-section">
+      <div class="test-header">
+        <h3>📊 Test Results</h3>
+        <div id="testSummary">
+          <span class="badge bg-secondary">Ready</span>
+        </div>
+      </div>
+      
+      <div class="table-responsive">
+        <table class="table table-sm">
+          <thead>
+            <tr>
+              <th>Test</th>
+              <th>Status</th>
+              <th>Duration</th>
+              <th>Details</th>
+            </tr>
+          </thead>
+          <tbody id="testResultsTable">
+            <tr>
+              <td colspan="4" class="text-center text-muted">No tests run yet</td>
+            </tr>
+          </tbody>
+        </table>
+      </div>
+    </div>
+    
+    <!-- Calendar UI Demo -->
+    <div class="test-section">
+      <div class="test-header">
+        <h3>📅 Calendar UI Demo</h3>
+        <button id="btnCreateCalendar" class="btn btn-sm btn-outline-primary" data-action="create-calendar">
+          <i class="bi-plus-lg"></i> Create Calendar
+        </button>
+      </div>
+      
+      <div class="row">
+        <div class="col-md-3">
+          <h5>My Calendars</h5>
+          <div id="calendarListContainer" class="calendar-list-container">
+            <div class="text-center text-muted py-3">
+              <div class="spinner-border spinner-border-sm" role="status">
+                <span class="visually-hidden">Loading...</span>
+              </div>
+              <p class="mb-0 mt-2">Loading calendars...</p>
+            </div>
+          </div>
+        </div>
+        <div class="col-md-9">
+          <div id="calendarContainer"></div>
+        </div>
+      </div>
+    </div>
+    
+    <!-- Console Log -->
+    <div class="test-section">
+      <div class="test-header">
+        <h3>📝 Console Log</h3>
+        <button id="toggleConsole" class="btn btn-sm btn-outline-secondary">
+          <i class="bi-chevron-up"></i> Collapse
+        </button>
+      </div>
+      <div id="logConsole" class="log-console"></div>
+    </div>
+  </div>
+  
+  <!-- Modal Template -->
+  <div class="modal fade" id="calendarManageModal" tabindex="-1" aria-hidden="true">
+    <div class="modal-dialog">
+      <div class="modal-content">
+        <div class="modal-header">
+          <h5 class="modal-title">Manage Calendar</h5>
+          <button type="button" class="btn-close" data-bs-dismiss="modal" aria-label="Close"></button>
+        </div>
+        <div class="modal-body">
+          <form id="calendarForm">
+            <div class="mb-3">
+              <label for="calendarTitle" class="form-label">Title</label>
+              <input type="text" class="form-control" id="calendarTitle" required>
+            </div>
+            <div class="mb-3">
+              <label for="calendarDescription" class="form-label">Description</label>
+              <textarea class="form-control" id="calendarDescription" rows="3"></textarea>
+            </div>
+            <div class="mb-3">
+              <label for="calendarColor" class="form-label">Color</label>
+              <input type="color" class="form-control form-control-color" id="calendarColor" value="#0d6efd">
+            </div>
+            <div class="mb-3">
+              <label class="form-label">Type</label>
+              <div>
+                <div class="form-check">
+                  <input class="form-check-input" type="radio" name="calendarType" id="typePersonal" value="personal" checked>
+                  <label class="form-check-label" for="typePersonal">Personal</label>
+                </div>
+                <div class="form-check">
+                  <input class="form-check-input" type="radio" name="calendarType" id="typePublic" value="public">
+                  <label class="form-check-label" for="typePublic">Public</label>
+                </div>
+              </div>
+            </div>
+          </form>
+        </div>
+        <div class="modal-footer">
+          <button type="button" class="btn btn-secondary" data-bs-dismiss="modal">Cancel</button>
+          <button type="button" class="btn btn-primary" id="saveCalendarBtn">Save</button>
+        </div>
+      </div>
+    </div>
+  </div>
+  
+  <!-- Bootstrap JS -->
+  <script src="https://cdn.jsdelivr.net/npm/bootstrap@5.3.0/dist/js/bootstrap.bundle.min.js"></script>
+  <!-- FullCalendar JS -->
+  <script src="https://cdn.jsdelivr.net/npm/fullcalendar@6.1.8/index.global.min.js"></script>
+  
+  <script>
+    // =========================
+    // Mock Data & API
+    // =========================
+    
+    let mockCalendars = [
+      { id: 1, title: 'Personal', description: 'My personal calendar', color: '#0d6efd', calendar_type: 'personal', user_can_edit: true, user_can_view: true, is_subscribed: true },
+      { id: 2, title: 'Work', description: 'Work events', color: '#198754', calendar_type: 'public', user_can_edit: true, user_can_view: true, is_subscribed: true },
+      { id: 3, title: 'Team Meetings', description: 'Team sync meetings', color: '#ffc107', calendar_type: 'department', user_can_edit: false, user_can_view: true, is_subscribed: true },
+    ];
+    
+    let mockEvents = [
+      { id: 1, title: 'Morning Standup', start: new Date(2026, 1, 11, 9, 0), end: new Date(2026, 1, 11, 9, 30), color: '#0d6efd', calendar_id: 1 },
+      { id: 2, title: 'Client Meeting', start: new Date(2026, 1, 11, 14, 0), end: new Date(2026, 1, 11, 15, 0), color: '#198754', calendar_id: 2 },
+      { id: 3, title: 'Sprint Planning', start: new Date(2026, 1, 12, 10, 0), end: new Date(2026, 1, 12, 12, 0), color: '#ffc107', calendar_id: 3 },
+      { id: 4, title: 'Code Review', start: new Date(2026, 1, 13, 15, 0), end: new Date(2026, 1, 13, 16, 0), color: '#0d6efd', calendar_id: 1 },
+    ];
+    
+    // Mock API
+    const mockAPI = {
+      getMyCalendars: async () => {
+        await delay(300);
+        log('API: getMyCalendars() → ' + mockCalendars.length + ' calendars', 'info');
+        return { ok: true, data: [...mockCalendars] };
+      },
+      
+      createCalendar: async (data) => {
+        await delay(500);
+        const newCalendar = {
+          id: Date.now(),
+          ...data,
+          user_can_edit: true,
+          user_can_view: true,
+          is_subscribed: true
+        };
+        mockCalendars.push(newCalendar);
+        log('API: createCalendar() → Calendar #' + newCalendar.id + ' created', 'success');
+        return { ok: true, data: newCalendar };
+      },
+      
+      updateCalendar: async (id, data) => {
+        await delay(500);
+        const index = mockCalendars.findIndex(c => c.id === id);
+        if (index !== -1) {
+          mockCalendars[index] = { ...mockCalendars[index], ...data };
+          log('API: updateCalendar(' + id + ') → Updated', 'success');
+          return { ok: true, data: mockCalendars[index] };
+        }
+        return { ok: false, error: 'Calendar not found' };
+      },
+      
+      deleteCalendar: async (id) => {
+        await delay(500);
+        mockCalendars = mockCalendars.filter(c => c.id !== id);
+        log('API: deleteCalendar(' + id + ') → Deleted', 'success');
+        return { ok: true };
+      },
+      
+      getCalendarEvents: async (params) => {
+        await delay(300);
+        let events = [...mockEvents];
+        if (params.calendar_id) {
+          events = events.filter(e => e.calendar_id === params.calendar_id);
+        }
+        log('API: getCalendarEvents(' + JSON.stringify(params) + ') → ' + events.length + ' events', 'info');
+        return { ok: true, data: events };
+      }
+    };
+    
+    // =========================
+    // Test Logger
+    // =========================
+    
+    const logConsole = document.getElementById('logConsole');
+    const testResultsTable = document.getElementById('testResultsTable');
+    let testResults = [];
+    
+    function log(message, type = 'info') {
+      const timestamp = new Date().toLocaleTimeString();
+      const entry = document.createElement('div');
+      entry.className = 'log-entry log-' + type;
+      entry.textContent = '[' + timestamp + '] ' + message;
+      logConsole.appendChild(entry);
+      logConsole.scrollTop = logConsole.scrollHeight;
+      
+      // Also log to real console
+      console.log('[Test]', message);
+    }
+    
+    function delay(ms) {
+      return new Promise(resolve => setTimeout(resolve, ms));
+    }
+    
+    function updateTestResult(testName, status, duration, details) {
+      testResults.push({ testName, status, duration, details });
+      renderTestResults();
+    }
+    
+    function renderTestResults() {
+      if (testResults.length === 0) {
+        testResultsTable.innerHTML = '<tr><td colspan="4" class="text-center text-muted">No tests run yet</td></tr>';
+        return;
+      }
+      
+      testResultsTable.innerHTML = testResults.map(result => `
+        <tr>
+          <td>${result.testName}</td>
+          <td><span class="badge bg-${result.status === 'passed' ? 'success' : 'danger'}">${result.status}</span></td>
+          <td>${result.duration}ms</td>
+          <td class="text-muted small">${result.details}</td>
+        </tr>
+      `).join('');
+      
+      const passed = testResults.filter(r => r.status === 'passed').length;
+      const failed = testResults.filter(r => r.status === 'failed').length;
+      document.getElementById('testSummary').innerHTML = `
+        <span class="badge bg-success">${passed} Passed</span>
+        <span class="badge bg-danger">${failed} Failed</span>
+      `;
+    }
+    
+    // =========================
+    // Tests
+    // =========================
+    
+    async function testApiWrapper() {
+      log('=== Test 1: API Wrapper ===', 'info');
+      const startTime = Date.now();
+      
+      try {
+        // Test getMyCalendars
+        const calendars = await mockAPI.getMyCalendars();
+        if (!calendars.ok || !Array.isArray(calendars.data)) {
+          throw new Error('getMyCalendars failed');
+        }
+        log('✓ getMyCalendars works', 'success');
+        
+        // Test createCalendar
+        const newCal = await mockAPI.createCalendar({
+          title: 'Test Calendar',
+          description: 'Test',
+          color: '#ff0000',
+          calendar_type: 'personal'
+        });
+        if (!newCal.ok || !newCal.data.id) {
+          throw new Error('createCalendar failed');
+        }
+        log('✓ createCalendar works', 'success');
+        
+        // Test getCalendarEvents
+        const events = await mockAPI.getCalendarEvents({ calendar_id: 1 });
+        if (!events.ok || !Array.isArray(events.data)) {
+          throw new Error('getCalendarEvents failed');
+        }
+        log('✓ getCalendarEvents works', 'success');
+        
+        const duration = Date.now() - startTime;
+        updateTestResult('API Wrapper', 'passed', duration, 'All API methods working');
+        log('✅ Test 1: PASSED', 'success');
+      } catch (error) {
+        const duration = Date.now() - startTime;
+        updateTestResult('API Wrapper', 'failed', duration, error.message);
+        log('❌ Test 1: FAILED - ' + error.message, 'error');
+      }
+    }
+    
+    async function testCalendarManager() {
+      log('=== Test 2: Calendar Manager ===', 'info');
+      const startTime = Date.now();
+      
+      try {
+        // Render calendar list
+        const calendars = await mockAPI.getMyCalendars();
+        const container = document.getElementById('calendarListContainer');
+        
+        container.innerHTML = calendars.data.map(cal => `
+          <div class="calendar-list-item" data-calendar-id="${cal.id}">
+            <input type="checkbox" class="form-check-input" ${cal.is_subscribed ? 'checked' : ''}>
+            <div class="calendar-color-indicator" style="background-color: ${cal.color}"></div>
+            <div class="calendar-list-item-info">
+              <p class="calendar-list-item-title">${cal.title}</p>
+              <p class="calendar-list-item-meta">${cal.calendar_type}</p>
+            </div>
+            <div class="calendar-list-item-actions">
+              ${cal.user_can_edit ? '<button class="btn btn-sm btn-outline-secondary"><i class="bi-pencil"></i></button>' : ''}
+            </div>
+          </div>
+        `).join('');
+        
+        log('✓ Calendar list rendered', 'success');
+        
+        // Test checkbox interaction
+        const firstCheckbox = container.querySelector('input[type="checkbox"]');
+        if (!firstCheckbox) {
+          throw new Error('Checkbox not found');
+        }
+        firstCheckbox.click();
+        log('✓ Checkbox interaction works', 'success');
+        
+        const duration = Date.now() - startTime;
+        updateTestResult('Calendar Manager', 'passed', duration, 'List rendering and interaction OK');
+        log('✅ Test 2: PASSED', 'success');
+      } catch (error) {
+        const duration = Date.now() - startTime;
+        updateTestResult('Calendar Manager', 'failed', duration, error.message);
+        log('❌ Test 2: FAILED - ' + error.message, 'error');
+      }
+    }
+    
+    async function testModalComponent() {
+      log('=== Test 3: Modal Component ===', 'info');
+      const startTime = Date.now();
+      
+      try {
+        const modal = new bootstrap.Modal(document.getElementById('calendarManageModal'));
+        
+        // Test modal open
+        modal.show();
+        await delay(500);
+        log('✓ Modal opens', 'success');
+        
+        // Test form validation
+        const titleInput = document.getElementById('calendarTitle');
+        titleInput.value = 'Test Calendar';
+        if (titleInput.value !== 'Test Calendar') {
+          throw new Error('Form input failed');
+        }
+        log('✓ Form inputs work', 'success');
+        
+        // Close modal
+        modal.hide();
+        await delay(500);
+        log('✓ Modal closes', 'success');
+        
+        const duration = Date.now() - startTime;
+        updateTestResult('Modal Component', 'passed', duration, 'Modal and form working');
+        log('✅ Test 3: PASSED', 'success');
+      } catch (error) {
+        const duration = Date.now() - startTime;
+        updateTestResult('Modal Component', 'failed', duration, error.message);
+        log('❌ Test 3: FAILED - ' + error.message, 'error');
+      }
+    }
+    
+    async function testWidgetIntegration() {
+      log('=== Test 4: Widget Integration ===', 'info');
+      const startTime = Date.now();
+      
+      try {
+        // Initialize FullCalendar
+        const calendarEl = document.getElementById('calendarContainer');
+        const calendar = new FullCalendar.Calendar(calendarEl, {
+          initialView: 'dayGridMonth',
+          initialDate: '2026-02-11',
+          events: async (info, success, failure) => {
+            try {
+              const events = await mockAPI.getCalendarEvents({});
+              success(events.data);
+            } catch (e) {
+              failure(e);
+            }
+          }
+        });
+        
+        calendar.render();
+        await delay(1000);
+        log('✓ FullCalendar initialized', 'success');
+        
+        // Check if events loaded
+        const eventCount = calendar.getEvents().length;
+        if (eventCount === 0) {
+          throw new Error('No events loaded');
+        }
+        log('✓ Events loaded: ' + eventCount, 'success');
+        
+        const duration = Date.now() - startTime;
+        updateTestResult('Widget Integration', 'passed', duration, eventCount + ' events loaded');
+        log('✅ Test 4: PASSED', 'success');
+      } catch (error) {
+        const duration = Date.now() - startTime;
+        updateTestResult('Widget Integration', 'failed', duration, error.message);
+        log('❌ Test 4: FAILED - ' + error.message, 'error');
+      }
+    }
+    
+    async function testEventFiltering() {
+      log('=== Test 5: Event Filtering ===', 'info');
+      const startTime = Date.now();
+      
+      try {
+        // Test filtering by calendar_id
+        const allEvents = await mockAPI.getCalendarEvents({});
+        const filteredEvents = await mockAPI.getCalendarEvents({ calendar_id: 1 });
+        
+        if (filteredEvents.data.length >= allEvents.data.length) {
+          throw new Error('Filtering not working');
+        }
+        log('✓ Calendar filtering works', 'success');
+        log('  All events: ' + allEvents.data.length, 'info');
+        log('  Filtered (calendar 1): ' + filteredEvents.data.length, 'info');
+        
+        const duration = Date.now() - startTime;
+        updateTestResult('Event Filtering', 'passed', duration, 'Filtering by calendar_id works');
+        log('✅ Test 5: PASSED', 'success');
+      } catch (error) {
+        const duration = Date.now() - startTime;
+        updateTestResult('Event Filtering', 'failed', duration, error.message);
+        log('❌ Test 5: FAILED - ' + error.message, 'error');
+      }
+    }
+    
+    async function testUserInteractions() {
+      log('=== Test 6: User Interactions ===', 'info');
+      const startTime = Date.now();
+      
+      try {
+        // Test create button
+        const createBtn = document.getElementById('btnCreateCalendar');
+        if (!createBtn) {
+          throw new Error('Create button not found');
+        }
+        log('✓ Create button exists', 'success');
+        
+        // Test calendar list items
+        const calendarItems = document.querySelectorAll('.calendar-list-item');
+        if (calendarItems.length === 0) {
+          throw new Error('No calendar items found');
+        }
+        log('✓ Calendar items rendered: ' + calendarItems.length, 'success');
+        
+        // Test checkboxes
+        const checkboxes = document.querySelectorAll('.calendar-list-item input[type="checkbox"]');
+        if (checkboxes.length === 0) {
+          throw new Error('No checkboxes found');
+        }
+        log('✓ Checkboxes present: ' + checkboxes.length, 'success');
+        
+        const duration = Date.now() - startTime;
+        updateTestResult('User Interactions', 'passed', duration, 'All UI elements interactive');
+        log('✅ Test 6: PASSED', 'success');
+      } catch (error) {
+        const duration = Date.now() - startTime;
+        updateTestResult('User Interactions', 'failed', duration, error.message);
+        log('❌ Test 6: FAILED - ' + error.message, 'error');
+      }
+    }
+    
+    // =========================
+    // Event Listeners
+    // =========================
+    
+    document.getElementById('runAllTests').addEventListener('click', async () => {
+      testResults = [];
+      log('🚀 Running all tests...', 'info');
+      
+      await testApiWrapper();
+      await delay(500);
+      await testCalendarManager();
+      await delay(500);
+      await testModalComponent();
+      await delay(500);
+      await testWidgetIntegration();
+      await delay(500);
+      await testEventFiltering();
+      await delay(500);
+      await testUserInteractions();
+      
+      log('🏁 All tests completed!', 'success');
+    });
+    
+    document.getElementById('clearLogs').addEventListener('click', () => {
+      logConsole.innerHTML = '';
+      log('Logs cleared', 'info');
+    });
+    
+    document.getElementById('toggleConsole').addEventListener('click', () => {
+      const console = document.getElementById('logConsole');
+      const btn = document.getElementById('toggleConsole');
+      if (console.style.display === 'none') {
+        console.style.display = 'block';
+        btn.innerHTML = '<i class="bi-chevron-up"></i> Collapse';
+      } else {
+        console.style.display = 'none';
+        btn.innerHTML = '<i class="bi-chevron-down"></i> Expand';
+      }
+    });
+    
+    document.getElementById('testApiWrapper').addEventListener('click', testApiWrapper);
+    document.getElementById('testCalendarManager').addEventListener('click', testCalendarManager);
+    document.getElementById('testModalComponent').addEventListener('click', testModalComponent);
+    document.getElementById('testWidgetIntegration').addEventListener('click', testWidgetIntegration);
+    document.getElementById('testEventFiltering').addEventListener('click', testEventFiltering);
+    document.getElementById('testUserInteractions').addEventListener('click', testUserInteractions);
+    
+    // Modal save button
+    document.getElementById('saveCalendarBtn').addEventListener('click', async () => {
+      const title = document.getElementById('calendarTitle').value;
+      const description = document.getElementById('calendarDescription').value;
+      const color = document.getElementById('calendarColor').value;
+      const type = document.querySelector('input[name="calendarType"]:checked').value;
+      
+      if (!title) {
+        alert('Title is required');
+        return;
+      }
+      
+      log('Creating calendar: ' + title, 'info');
+      const result = await mockAPI.createCalendar({ title, description, color, calendar_type: type });
+      
+      if (result.ok) {
+        log('Calendar created successfully!', 'success');
+        const modal = bootstrap.Modal.getInstance(document.getElementById('calendarManageModal'));
+        modal.hide();
+        
+        // Refresh calendar list
+        await testCalendarManager();
+      }
+    });
+    
+    // Create calendar button
+    document.getElementById('btnCreateCalendar').addEventListener('click', () => {
+      log('Opening create calendar modal', 'info');
+      const modal = new bootstrap.Modal(document.getElementById('calendarManageModal'));
+      
+      // Reset form
+      document.getElementById('calendarTitle').value = '';
+      document.getElementById('calendarDescription').value = '';
+      document.getElementById('calendarColor').value = '#0d6efd';
+      document.getElementById('typePersonal').checked = true;
+      
+      modal.show();
+    });
+    
+    // =========================
+    // Initialize
+    // =========================
+    
+    log('✅ Test suite initialized', 'success');
+    log('Click "Run All Tests" to start', 'info');
+    
+    // Auto-load calendar list on startup (wrapped in async IIFE)
+    (async function init() {
+      try {
+        await testCalendarManager();
+        await testWidgetIntegration();
+      } catch (error) {
+        log('Initialization error: ' + error.message, 'error');
+      }
+    })();
+  </script>
+</body>
+</html>
diff --git a/backend/test_calendar_frontend_simple.html b/backend/test_calendar_frontend_simple.html
new file mode 100644
index 00000000..3a8016fb
--- /dev/null
+++ b/backend/test_calendar_frontend_simple.html
@@ -0,0 +1,720 @@
+<!DOCTYPE html>
+<html lang="ru">
+<head>
+  <meta charset="UTF-8">
+  <meta name="viewport" content="width=device-width, initial-scale=1.0">
+  <title>Calendar Frontend Test - Simple Version</title>
+  
+  <style>
+    * {
+      margin: 0;
+      padding: 0;
+      box-sizing: border-box;
+    }
+    
+    body {
+      font-family: -apple-system, BlinkMacSystemFont, 'Segoe UI', Arial, sans-serif;
+      padding: 20px;
+      background: #f5f5f5;
+      line-height: 1.6;
+    }
+    
+    .container {
+      max-width: 1200px;
+      margin: 0 auto;
+    }
+    
+    h1 {
+      color: #333;
+      margin-bottom: 20px;
+    }
+    
+    .test-section {
+      background: white;
+      border-radius: 8px;
+      padding: 20px;
+      margin-bottom: 20px;
+      box-shadow: 0 2px 4px rgba(0,0,0,0.1);
+    }
+    
+    .test-header {
+      display: flex;
+      justify-content: space-between;
+      align-items: center;
+      margin-bottom: 15px;
+      padding-bottom: 15px;
+      border-bottom: 2px solid #e9ecef;
+    }
+    
+    h2 {
+      font-size: 20px;
+      color: #333;
+    }
+    
+    button {
+      padding: 8px 16px;
+      border: none;
+      border-radius: 4px;
+      cursor: pointer;
+      font-size: 14px;
+      transition: all 0.2s;
+    }
+    
+    .btn-primary {
+      background: #0d6efd;
+      color: white;
+    }
+    
+    .btn-primary:hover {
+      background: #0b5ed7;
+    }
+    
+    .btn-secondary {
+      background: #6c757d;
+      color: white;
+      margin-left: 10px;
+    }
+    
+    .btn-secondary:hover {
+      background: #5c636a;
+    }
+    
+    .btn-outline {
+      background: white;
+      border: 1px solid #dee2e6;
+      color: #333;
+      padding: 10px;
+      margin: 5px;
+      width: calc(33.33% - 10px);
+      display: inline-block;
+    }
+    
+    .btn-outline:hover {
+      background: #f8f9fa;
+      border-color: #0d6efd;
+    }
+    
+    .test-controls {
+      display: flex;
+      flex-wrap: wrap;
+    }
+    
+    table {
+      width: 100%;
+      border-collapse: collapse;
+    }
+    
+    th, td {
+      padding: 10px;
+      text-align: left;
+      border-bottom: 1px solid #dee2e6;
+    }
+    
+    th {
+      background: #f8f9fa;
+      font-weight: 600;
+    }
+    
+    .badge {
+      padding: 4px 8px;
+      border-radius: 4px;
+      font-size: 12px;
+      font-weight: bold;
+    }
+    
+    .badge-success {
+      background: #28a745;
+      color: white;
+    }
+    
+    .badge-danger {
+      background: #dc3545;
+      color: white;
+    }
+    
+    .badge-secondary {
+      background: #6c757d;
+      color: white;
+    }
+    
+    .log-console {
+      background: #2d2d2d;
+      color: #f8f8f2;
+      padding: 15px;
+      border-radius: 4px;
+      font-family: 'Courier New', monospace;
+      font-size: 13px;
+      max-height: 400px;
+      overflow-y: auto;
+    }
+    
+    .log-entry {
+      margin: 3px 0;
+      padding: 2px 0;
+    }
+    
+    .log-info { color: #66d9ef; }
+    .log-success { color: #a6e22e; }
+    .log-error { color: #f92672; }
+    .log-warn { color: #e6db74; }
+    
+    .calendar-list {
+      border: 1px solid #dee2e6;
+      border-radius: 4px;
+      padding: 10px;
+      max-height: 400px;
+      overflow-y: auto;
+    }
+    
+    .calendar-item {
+      padding: 10px;
+      margin-bottom: 8px;
+      border: 1px solid #e9ecef;
+      border-radius: 4px;
+      display: flex;
+      align-items: center;
+      gap: 10px;
+      background: white;
+    }
+    
+    .calendar-item:hover {
+      background: #f8f9fa;
+      border-color: #0d6efd;
+    }
+    
+    .calendar-color {
+      width: 12px;
+      height: 12px;
+      border-radius: 50%;
+      border: 2px solid rgba(0,0,0,0.1);
+    }
+    
+    .calendar-info {
+      flex: 1;
+    }
+    
+    .calendar-title {
+      font-weight: 600;
+      font-size: 14px;
+    }
+    
+    .calendar-meta {
+      font-size: 12px;
+      color: #6c757d;
+    }
+    
+    .text-muted {
+      color: #6c757d;
+    }
+    
+    .text-center {
+      text-align: center;
+    }
+    
+    input[type="checkbox"] {
+      width: 18px;
+      height: 18px;
+      cursor: pointer;
+    }
+  </style>
+</head>
+<body>
+  <div class="container">
+    <h1>🧪 Calendar Frontend Test Suite (Offline Version)</h1>
+    
+    <!-- Test Controls -->
+    <div class="test-section">
+      <div class="test-header">
+        <h2>🎮 Test Controls</h2>
+        <div>
+          <button id="runAllTests" class="btn-primary">▶ Run All Tests</button>
+          <button id="clearLogs" class="btn-secondary">🗑 Clear Logs</button>
+        </div>
+      </div>
+      
+      <div class="test-controls">
+        <button class="btn-outline" onclick="testApiWrapper()">Test 1: API Wrapper</button>
+        <button class="btn-outline" onclick="testCalendarManager()">Test 2: Calendar Manager</button>
+        <button class="btn-outline" onclick="testEventFiltering()">Test 3: Event Filtering</button>
+        <button class="btn-outline" onclick="testStateManagement()">Test 4: State Management</button>
+        <button class="btn-outline" onclick="testCallbacks()">Test 5: Callbacks</button>
+        <button class="btn-outline" onclick="testDataStructures()">Test 6: Data Structures</button>
+      </div>
+    </div>
+    
+    <!-- Test Results -->
+    <div class="test-section">
+      <div class="test-header">
+        <h2>📊 Test Results</h2>
+        <div id="testSummary">
+          <span class="badge badge-secondary">Ready</span>
+        </div>
+      </div>
+      
+      <table>
+        <thead>
+          <tr>
+            <th>Test</th>
+            <th>Status</th>
+            <th>Duration</th>
+            <th>Details</th>
+          </tr>
+        </thead>
+        <tbody id="testResultsTable">
+          <tr>
+            <td colspan="4" class="text-center text-muted">No tests run yet</td>
+          </tr>
+        </tbody>
+      </table>
+    </div>
+    
+    <!-- Calendar UI Demo -->
+    <div class="test-section">
+      <div class="test-header">
+        <h2>📅 Calendar List Demo</h2>
+        <button class="btn-primary" onclick="createCalendar()">➕ Create Calendar</button>
+      </div>
+      
+      <div id="calendarListContainer" class="calendar-list">
+        <div class="text-center text-muted">Loading calendars...</div>
+      </div>
+    </div>
+    
+    <!-- Console Log -->
+    <div class="test-section">
+      <div class="test-header">
+        <h2>📝 Console Log</h2>
+        <button class="btn-secondary" onclick="toggleConsole()">▲ Toggle</button>
+      </div>
+      <div id="logConsole" class="log-console"></div>
+    </div>
+  </div>
+  
+  <script>
+    // =========================
+    // State Management
+    // =========================
+    
+    let mockCalendars = [
+      { id: 1, title: 'Personal', description: 'My personal calendar', color: '#0d6efd', calendar_type: 'personal', user_can_edit: true, user_can_view: true, is_subscribed: true, visible: true },
+      { id: 2, title: 'Work', description: 'Work events', color: '#198754', calendar_type: 'public', user_can_edit: true, user_can_view: true, is_subscribed: true, visible: true },
+      { id: 3, title: 'Team Meetings', description: 'Team sync', color: '#ffc107', calendar_type: 'department', user_can_edit: false, user_can_view: true, is_subscribed: true, visible: false },
+    ];
+    
+    let mockEvents = [
+      { id: 1, title: 'Morning Standup', start: '2026-02-11T09:00', end: '2026-02-11T09:30', color: '#0d6efd', calendar_id: 1 },
+      { id: 2, title: 'Client Meeting', start: '2026-02-11T14:00', end: '2026-02-11T15:00', color: '#198754', calendar_id: 2 },
+      { id: 3, title: 'Sprint Planning', start: '2026-02-12T10:00', end: '2026-02-12T12:00', color: '#ffc107', calendar_id: 3 },
+      { id: 4, title: 'Code Review', start: '2026-02-13T15:00', end: '2026-02-13T16:00', color: '#0d6efd', calendar_id: 1 },
+    ];
+    
+    let testResults = [];
+    let visibleCalendarIds = [1, 2];
+    
+    // =========================
+    // Logger
+    // =========================
+    
+    function log(message, type = 'info') {
+      const timestamp = new Date().toLocaleTimeString();
+      const logConsole = document.getElementById('logConsole');
+      const entry = document.createElement('div');
+      entry.className = 'log-entry log-' + type;
+      entry.textContent = '[' + timestamp + '] ' + message;
+      logConsole.appendChild(entry);
+      logConsole.scrollTop = logConsole.scrollHeight;
+      console.log('[Test]', message);
+    }
+    
+    function delay(ms) {
+      return new Promise(resolve => setTimeout(resolve, ms));
+    }
+    
+    function updateTestResult(testName, status, duration, details) {
+      testResults.push({ testName, status, duration, details });
+      renderTestResults();
+    }
+    
+    function renderTestResults() {
+      const tbody = document.getElementById('testResultsTable');
+      
+      if (testResults.length === 0) {
+        tbody.innerHTML = '<tr><td colspan="4" class="text-center text-muted">No tests run yet</td></tr>';
+        return;
+      }
+      
+      tbody.innerHTML = testResults.map(r => `
+        <tr>
+          <td>${r.testName}</td>
+          <td><span class="badge badge-${r.status === 'passed' ? 'success' : 'danger'}">${r.status.toUpperCase()}</span></td>
+          <td>${r.duration}ms</td>
+          <td class="text-muted">${r.details}</td>
+        </tr>
+      `).join('');
+      
+      const passed = testResults.filter(r => r.status === 'passed').length;
+      const failed = testResults.filter(r => r.status === 'failed').length;
+      document.getElementById('testSummary').innerHTML = `
+        <span class="badge badge-success">${passed} Passed</span>
+        <span class="badge badge-danger">${failed} Failed</span>
+      `;
+    }
+    
+    // =========================
+    // Mock API
+    // =========================
+    
+    async function mockApiGetCalendars() {
+      await delay(200);
+      return { ok: true, data: [...mockCalendars] };
+    }
+    
+    async function mockApiGetEvents(calendarId = null) {
+      await delay(150);
+      let events = [...mockEvents];
+      if (calendarId) {
+        events = events.filter(e => e.calendar_id === calendarId);
+      }
+      return { ok: true, data: events };
+    }
+    
+    async function mockApiCreateCalendar(data) {
+      await delay(300);
+      const newCal = {
+        id: Date.now(),
+        ...data,
+        user_can_edit: true,
+        user_can_view: true,
+        is_subscribed: true,
+        visible: true
+      };
+      mockCalendars.push(newCal);
+      return { ok: true, data: newCal };
+    }
+    
+    // =========================
+    // Tests
+    // =========================
+    
+    async function testApiWrapper() {
+      log('=== Test 1: API Wrapper ===', 'info');
+      const startTime = Date.now();
+      
+      try {
+        const calendars = await mockApiGetCalendars();
+        if (!calendars.ok || !Array.isArray(calendars.data)) {
+          throw new Error('getCalendars failed');
+        }
+        log('✓ mockApiGetCalendars() → ' + calendars.data.length + ' calendars', 'success');
+        
+        const events = await mockApiGetEvents(1);
+        if (!events.ok || !Array.isArray(events.data)) {
+          throw new Error('getEvents failed');
+        }
+        log('✓ mockApiGetEvents(1) → ' + events.data.length + ' events', 'success');
+        
+        const allEvents = await mockApiGetEvents();
+        log('✓ mockApiGetEvents() → ' + allEvents.data.length + ' total events', 'success');
+        
+        const duration = Date.now() - startTime;
+        updateTestResult('API Wrapper', 'passed', duration, 'All API methods working');
+        log('✅ Test 1: PASSED', 'success');
+      } catch (error) {
+        const duration = Date.now() - startTime;
+        updateTestResult('API Wrapper', 'failed', duration, error.message);
+        log('❌ Test 1: FAILED - ' + error.message, 'error');
+      }
+    }
+    
+    async function testCalendarManager() {
+      log('=== Test 2: Calendar Manager ===', 'info');
+      const startTime = Date.now();
+      
+      try {
+        const calendars = await mockApiGetCalendars();
+        renderCalendarList(calendars.data);
+        
+        const container = document.getElementById('calendarListContainer');
+        const items = container.querySelectorAll('.calendar-item');
+        
+        if (items.length !== calendars.data.length) {
+          throw new Error('Calendar count mismatch: ' + items.length + ' != ' + calendars.data.length);
+        }
+        log('✓ Rendered ' + items.length + ' calendar items', 'success');
+        
+        const checkboxes = container.querySelectorAll('input[type="checkbox"]');
+        if (checkboxes.length === 0) {
+          throw new Error('No checkboxes found');
+        }
+        log('✓ ' + checkboxes.length + ' checkboxes created', 'success');
+        
+        const duration = Date.now() - startTime;
+        updateTestResult('Calendar Manager', 'passed', duration, 'List rendering OK');
+        log('✅ Test 2: PASSED', 'success');
+      } catch (error) {
+        const duration = Date.now() - startTime;
+        updateTestResult('Calendar Manager', 'failed', duration, error.message);
+        log('❌ Test 2: FAILED - ' + error.message, 'error');
+      }
+    }
+    
+    async function testEventFiltering() {
+      log('=== Test 3: Event Filtering ===', 'info');
+      const startTime = Date.now();
+      
+      try {
+        const allEvents = await mockApiGetEvents();
+        const filteredEvents = await mockApiGetEvents(1);
+        
+        if (filteredEvents.data.length >= allEvents.data.length) {
+          throw new Error('Filtering not working correctly');
+        }
+        log('✓ All events: ' + allEvents.data.length, 'info');
+        log('✓ Calendar 1 events: ' + filteredEvents.data.length, 'info');
+        
+        // Test visible calendar filtering
+        const visibleEvents = fetchEventsForVisibleCalendars(allEvents.data);
+        log('✓ Visible calendars: ' + visibleCalendarIds.join(', '), 'info');
+        log('✓ Visible events: ' + visibleEvents.length, 'info');
+        
+        const duration = Date.now() - startTime;
+        updateTestResult('Event Filtering', 'passed', duration, 'Filtering works correctly');
+        log('✅ Test 3: PASSED', 'success');
+      } catch (error) {
+        const duration = Date.now() - startTime;
+        updateTestResult('Event Filtering', 'failed', duration, error.message);
+        log('❌ Test 3: FAILED - ' + error.message, 'error');
+      }
+    }
+    
+    async function testStateManagement() {
+      log('=== Test 4: State Management ===', 'info');
+      const startTime = Date.now();
+      
+      try {
+        const initialVisible = [...visibleCalendarIds];
+        log('✓ Initial visible: ' + initialVisible.join(', '), 'info');
+        
+        // Toggle visibility
+        toggleCalendarVisibility(3, true);
+        if (!visibleCalendarIds.includes(3)) {
+          throw new Error('Calendar 3 not added to visible');
+        }
+        log('✓ Calendar 3 added to visible', 'success');
+        
+        toggleCalendarVisibility(3, false);
+        if (visibleCalendarIds.includes(3)) {
+          throw new Error('Calendar 3 not removed from visible');
+        }
+        log('✓ Calendar 3 removed from visible', 'success');
+        
+        const duration = Date.now() - startTime;
+        updateTestResult('State Management', 'passed', duration, 'State updates correctly');
+        log('✅ Test 4: PASSED', 'success');
+      } catch (error) {
+        const duration = Date.now() - startTime;
+        updateTestResult('State Management', 'failed', duration, error.message);
+        log('❌ Test 4: FAILED - ' + error.message, 'error');
+      }
+    }
+    
+    async function testCallbacks() {
+      log('=== Test 5: Callbacks ===', 'info');
+      const startTime = Date.now();
+      
+      try {
+        let callbackCalled = false;
+        
+        function testCallback(calendarId, isVisible) {
+          callbackCalled = true;
+          log('✓ Callback triggered: cal=' + calendarId + ', visible=' + isVisible, 'info');
+        }
+        
+        testCallback(1, true);
+        
+        if (!callbackCalled) {
+          throw new Error('Callback not called');
+        }
+        log('✓ Callback mechanism works', 'success');
+        
+        const duration = Date.now() - startTime;
+        updateTestResult('Callbacks', 'passed', duration, 'Callbacks working');
+        log('✅ Test 5: PASSED', 'success');
+      } catch (error) {
+        const duration = Date.now() - startTime;
+        updateTestResult('Callbacks', 'failed', duration, error.message);
+        log('❌ Test 5: FAILED - ' + error.message, 'error');
+      }
+    }
+    
+    async function testDataStructures() {
+      log('=== Test 6: Data Structures ===', 'info');
+      const startTime = Date.now();
+      
+      try {
+        // Test calendar structure
+        const cal = mockCalendars[0];
+        const requiredFields = ['id', 'title', 'color', 'calendar_type', 'user_can_edit', 'user_can_view'];
+        
+        for (const field of requiredFields) {
+          if (!(field in cal)) {
+            throw new Error('Missing field: ' + field);
+          }
+        }
+        log('✓ Calendar structure valid', 'success');
+        
+        // Test event structure
+        const event = mockEvents[0];
+        const eventFields = ['id', 'title', 'start', 'calendar_id'];
+        
+        for (const field of eventFields) {
+          if (!(field in event)) {
+            throw new Error('Missing event field: ' + field);
+          }
+        }
+        log('✓ Event structure valid', 'success');
+        
+        // Test deduplication
+        const duplicates = [...mockEvents, mockEvents[0]];
+        const unique = deduplicateEvents(duplicates);
+        if (unique.length !== mockEvents.length) {
+          throw new Error('Deduplication failed');
+        }
+        log('✓ Event deduplication works', 'success');
+        
+        const duration = Date.now() - startTime;
+        updateTestResult('Data Structures', 'passed', duration, 'All structures valid');
+        log('✅ Test 6: PASSED', 'success');
+      } catch (error) {
+        const duration = Date.now() - startTime;
+        updateTestResult('Data Structures', 'failed', duration, error.message);
+        log('❌ Test 6: FAILED - ' + error.message, 'error');
+      }
+    }
+    
+    // =========================
+    // Helper Functions
+    // =========================
+    
+    function fetchEventsForVisibleCalendars(allEvents) {
+      return allEvents.filter(e => visibleCalendarIds.includes(e.calendar_id));
+    }
+    
+    function toggleCalendarVisibility(calendarId, isVisible) {
+      if (isVisible) {
+        if (!visibleCalendarIds.includes(calendarId)) {
+          visibleCalendarIds.push(calendarId);
+        }
+      } else {
+        visibleCalendarIds = visibleCalendarIds.filter(id => id !== calendarId);
+      }
+      log('Visible calendars: ' + visibleCalendarIds.join(', '), 'info');
+    }
+    
+    function deduplicateEvents(events) {
+      const seen = new Set();
+      return events.filter(e => {
+        if (seen.has(e.id)) return false;
+        seen.add(e.id);
+        return true;
+      });
+    }
+    
+    function renderCalendarList(calendars) {
+      const container = document.getElementById('calendarListContainer');
+      
+      container.innerHTML = calendars.map(cal => `
+        <div class="calendar-item">
+          <input 
+            type="checkbox" 
+            ${cal.visible ? 'checked' : ''} 
+            onchange="handleCalendarToggle(${cal.id}, this.checked)"
+          >
+          <div class="calendar-color" style="background-color: ${cal.color}"></div>
+          <div class="calendar-info">
+            <div class="calendar-title">${cal.title}</div>
+            <div class="calendar-meta">${cal.calendar_type} ${cal.user_can_edit ? '✏️' : '👁️'}</div>
+          </div>
+        </div>
+      `).join('');
+    }
+    
+    function handleCalendarToggle(calendarId, isChecked) {
+      log('Calendar ' + calendarId + ' toggled: ' + isChecked, 'info');
+      toggleCalendarVisibility(calendarId, isChecked);
+      
+      // Update calendar state
+      const calendar = mockCalendars.find(c => c.id === calendarId);
+      if (calendar) {
+        calendar.visible = isChecked;
+      }
+    }
+    
+    function createCalendar() {
+      const title = prompt('Calendar title:');
+      if (!title) return;
+      
+      const color = '#' + Math.floor(Math.random()*16777215).toString(16);
+      
+      mockApiCreateCalendar({
+        title: title,
+        description: '',
+        color: color,
+        calendar_type: 'personal'
+      }).then(result => {
+        log('Calendar created: ' + result.data.title, 'success');
+        renderCalendarList(mockCalendars);
+      });
+    }
+    
+    function toggleConsole() {
+      const console = document.getElementById('logConsole');
+      console.style.display = console.style.display === 'none' ? 'block' : 'none';
+    }
+    
+    // =========================
+    // Event Listeners
+    // =========================
+    
+    document.getElementById('runAllTests').addEventListener('click', async () => {
+      testResults = [];
+      log('🚀 Running all tests...', 'info');
+      
+      await testApiWrapper();
+      await delay(300);
+      await testCalendarManager();
+      await delay(300);
+      await testEventFiltering();
+      await delay(300);
+      await testStateManagement();
+      await delay(300);
+      await testCallbacks();
+      await delay(300);
+      await testDataStructures();
+      
+      log('🏁 All tests completed!', 'success');
+    });
+    
+    document.getElementById('clearLogs').addEventListener('click', () => {
+      document.getElementById('logConsole').innerHTML = '';
+      log('Logs cleared', 'info');
+    });
+    
+    // =========================
+    // Initialize
+    // =========================
+    
+    (async function init() {
+      log('✅ Test suite initialized', 'success');
+      log('Click "Run All Tests" to start', 'info');
+      log('📡 Offline mode - using mock data', 'warn');
+      
+      try {
+        await testCalendarManager();
+      } catch (error) {
+        log('Init error: ' + error.message, 'error');
+      }
+    })();
+  </script>
+</body>
+</html>