diff --git a/lab2/main_test.js b/lab2/main_test.js
index 5034468..477b866 100644
--- a/lab2/main_test.js
+++ b/lab2/main_test.js
@@ -1,6 +1,77 @@
 const test = require('node:test');
 const assert = require('assert');
+const { mock } = require('node:test');  // 使用 node:test 內建 Mock
 const { Application, MailSystem } = require('./main');
 
-// TODO: write your tests here
-// Remember to use Stub, Mock, and Spy when necessary
\ No newline at end of file
+test("Test MailSystem's write method", () => {
+    const mailSystem = new MailSystem();
+    const result = mailSystem.write("Alice");
+    assert.strictEqual(result, "Congrats, Alice!");
+});
+
+test("Test MailSystem's send method with Stub", () => {
+    const mailSystem = new MailSystem();
+
+    // 使用 node:test 內建 mock 來 Stub `Math.random`
+    mock.method(global.Math, "random", () => 0.6);
+    assert.strictEqual(mailSystem.send("Bob", "Congrats, Bob!"), true);
+
+    mock.method(global.Math, "random", () => 0.4);
+    assert.strictEqual(mailSystem.send("Bob", "Congrats, Bob!"), false);
+});
+
+test("Test Application's getNames method with Stub", async () => {
+    // 先 Stub `Application.prototype.getNames()`，避免 `constructor()` 內部讀取檔案
+    mock.method(Application.prototype, 'getNames', async () => [["Alice", "Bob", "Charlie"], []]);
+
+    // **現在才建立 `Application` 物件**
+    const app = new Application();
+
+    // 呼叫 `getNames()`，確保它回傳 Stub 值
+    const [people, selected] = await app.getNames();
+
+    assert.deepStrictEqual(people, ["Alice", "Bob", "Charlie"]);
+    assert.deepStrictEqual(selected, []);
+});
+
+test("Test Application's selectNextPerson with Spy", () => {
+    // 先 Stub `getNames()` 避免 `constructor()` 內部讀取檔案
+    mock.method(Application.prototype, 'getNames', async () => [["Alice", "Bob", "Charlie"], []]);
+
+    // 創建 `Application` 實例
+    const app = new Application();
+
+    // 手動設置 `people` 和 `selected`
+    app.people = ["Alice", "Bob", "Charlie"];
+    app.selected = [];
+
+    // Spy `getRandomPerson`
+    const spy = mock.method(app, "getRandomPerson", () => "Bob");
+
+    // 測試 `selectNextPerson()`
+    const person1 = app.selectNextPerson();
+    assert.ok(spy.mock.calls.length > 0); // 確保 `getRandomPerson()` 被呼叫
+    assert.ok(app.selected.includes("Bob"));
+});
+
+test("Test Application's notifySelected using Mock", () => {
+    // 先 Stub `getNames()`，避免 `constructor()` 內部讀取 `name_list.txt`
+    mock.method(Application.prototype, 'getNames', async () => [["Alice", "Bob"], []]);
+
+    // 創建 `Application` 物件
+    const app = new Application();
+
+    // 手動設定 `selected`
+    app.selected = ["Alice", "Bob"];
+
+    // Mock `MailSystem.write()` 和 `send()`
+    const mockMailSystem = mock.method(app.mailSystem, "write", (name) => "Mocked content");
+    const mockSend = mock.method(app.mailSystem, "send", (name, content) => true);
+
+    // 測試 `notifySelected()`
+    app.notifySelected();
+
+    // 確保 Mock 方法被正確呼叫
+    assert.ok(mockMailSystem.mock.calls.length === 2);
+    assert.ok(mockSend.mock.calls.length === 2);
+});