add test file for clearAllCompleted function

src/module/test/clearAllCompleted.test.js

@@ -1 +1,64 @@
-import 'jest-localstorage-mock';
+import 'jest-localstorage-mock';
+
+import clearAllCompletedTasks from '../clearTask.js';
+import {
+  tasks,
+  storeTasksToLocalStorage,
+  deleteTask,
+} from '../taskFunctions.js';
+
+// Mock the localStorage and DOM elements
+jest.mock('../taskFunctions.js', () => ({
+  tasks: [
+    { description: 'Task 1', completed: false, index: 1 },
+    { description: 'Task 2', completed: false, index: 2 },
+    { description: 'Task 3', completed: false, index: 3 },
+  ],
+  storeTasksToLocalStorage: jest.fn(),
+  deleteTask: jest.fn(),
+  addTask: jest.fn(),
+  sortTasks: jest.fn(),
+}));
+
+const mockDisplayTasks = jest.fn();
+
+jest.mock('../../index.js', () => ({
+  displayTasks: mockDisplayTasks,
+}));
+
+const emptyTasks = [];
+
+describe('clearAllCompletedTasks', () => {
+  beforeEach(() => {
+    jest.clearAllMocks();
+  });
+
+  it('should clear all completed tasks', () => {
+    clearAllCompletedTasks(tasks);
+
+    expect(tasks.length).toBe(3);
+    expect(tasks[0].description).toBe('Task 1');
+    expect(tasks[0].completed).toBe(false);
+    expect(tasks[1].description).toBe('Task 2');
+    expect(tasks[1].completed).toBe(false);
+    expect(tasks[2].description).toBe('Task 3');
+    expect(tasks[2].completed).toBe(false);
+    expect(storeTasksToLocalStorage).toHaveBeenCalledTimes(1);
+  });
+
+  it('should not delete not completed tasks', () => {
+    tasks.forEach((task) => {
+      task.completed = false;
+    });
+
+    clearAllCompletedTasks(tasks);
+
+    expect(deleteTask).not.toHaveBeenCalled();
+  });
+
+  it('should not do anything if the list is empty', () => {
+    clearAllCompletedTasks(emptyTasks);
+
+    expect(emptyTasks.length).toBe(0);
+  });
+});