diff --git a/lab2/main_test.js b/lab2/main_test.js
index 5034468..34eb87a 100644
--- a/lab2/main_test.js
+++ b/lab2/main_test.js
@@ -3,4 +3,186 @@ const assert = require('assert');
 const { Application, MailSystem } = require('./main');
 
 // TODO: write your tests here
-// Remember to use Stub, Mock, and Spy when necessary
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+// Remember to use Stub, Mock, and Spy when necessary
+const fs = require('node:fs');
+const util = require('util');
+const writeFile = util.promisify(fs.writeFile);
+const unlinkFile = util.promisify(fs.unlink);
+
+async function createTestFile(content = "Alice\nBob\nCharlie") {
+  await writeFile("name_list.txt", content, 'utf-8');
+}
+
+async function removeTestFile() {
+  try {
+    await unlinkFile("name_list.txt");
+  } catch (error) {
+    // Ignore errors 
+  }
+}
+
+test.before(async () => {
+  await createTestFile();
+});
+
+test.after(async () => {
+  await removeTestFile();
+});
+
+// Tests for MailSystem class
+test('MailSystem.write should return congratulatory message', (t) => {
+  const mailSystem = new MailSystem();
+  const result = mailSystem.write('John');
+  assert.strictEqual(result, 'Congrats, John!');
+});
+
+test('MailSystem.send should return boolean indicating success', (t) => {
+  const mailSystem = new MailSystem();
+  
+  const originalRandom = Math.random;
+  
+  // Test success case
+  Math.random = () => 0.6; // return true 
+  const successResult = mailSystem.send('John', 'Congrats, John!');
+  assert.strictEqual(successResult, true);
+  
+  // Test failure case
+  Math.random = () => 0.4; // return false
+  const failureResult = mailSystem.send('John', 'Congrats, John!');
+  assert.strictEqual(failureResult, false);
+  
+  Math.random = originalRandom;
+});
+
+test('Application constructor should initialize properties', async (t) => {
+  await createTestFile("Alice\nBob\nCharlie");
+  const app = new Application();
+  
+  await new Promise(resolve => setTimeout(resolve, 10));
+  
+  assert.deepStrictEqual(app.people, ['Alice', 'Bob', 'Charlie']);
+  assert.deepStrictEqual(app.selected, []);
+  assert.ok(app.mailSystem instanceof MailSystem);
+});
+
+test('getNames should read and parse names from file', async (t) => {
+  await createTestFile("Dave\nEve\nFrank");
+  
+  const app = new Application();
+  const [people, selected] = await app.getNames();
+  
+  assert.deepStrictEqual(people, ['Dave', 'Eve', 'Frank']);
+  assert.deepStrictEqual(selected, []);
+});
+
+test('getRandomPerson should return a person from the people array', async (t) => {
+  const app = new Application();
+  
+  await new Promise(resolve => setTimeout(resolve, 10));
+  
+  app.people = ['Alice', 'Bob', 'Charlie'];
+  
+  const originalRandom = Math.random;
+  const originalFloor = Math.floor;
+  
+  // Create a spy 
+  let floorCallCount = 0;
+  Math.floor = (num) => {
+    floorCallCount++;
+    return originalFloor(num);
+  };
+  
+  Math.random = () => 0; //select idx 0 
+  assert.strictEqual(app.getRandomPerson(), 'Alice');
+  
+  Math.random = () => 0.34; // select idx 1 
+  assert.strictEqual(app.getRandomPerson(), 'Bob');
+  
+  Math.random = () => 0.67; // select idx 2 
+  assert.strictEqual(app.getRandomPerson(), 'Charlie');
+  
+  assert.strictEqual(floorCallCount, 3);
+  
+  Math.random = originalRandom;
+  Math.floor = originalFloor;
+});
+
+test('selectNextPerson should select a random unselected person', async (t) => {
+  const app = new Application();
+  await new Promise(resolve => setTimeout(resolve, 10));
+  
+  app.people = ['Alice', 'Bob', 'Charlie'];
+  app.selected = [];
+  
+  const originalGetRandomPerson = app.getRandomPerson;
+  let randomPersonCalls = 0;
+  
+  app.getRandomPerson = () => {
+    randomPersonCalls++;
+    if (randomPersonCalls === 1) return 'Bob';
+    if (randomPersonCalls === 2) return 'Bob'; 
+    if (randomPersonCalls === 3) return 'Alice'; 
+    return 'Charlie';
+  };
+  
+  const result = app.selectNextPerson();
+  assert.strictEqual(result, 'Bob');
+  assert.deepStrictEqual(app.selected, ['Bob']);
+  
+  const secondResult = app.selectNextPerson();
+  assert.strictEqual(secondResult, 'Alice');
+  assert.deepStrictEqual(app.selected, ['Bob', 'Alice']);
+  
+  app.getRandomPerson = originalGetRandomPerson;
+});
+
+test('selectNextPerson should return null when all people are selected', async (t) => {
+  const app = new Application();  
+  await new Promise(resolve => setTimeout(resolve, 10));
+  
+  app.people = ['Alice', 'Bob'];
+  app.selected = ['Alice', 'Bob'];
+  
+  const result = app.selectNextPerson();
+  
+  assert.strictEqual(result, null);
+});
+
+test('notifySelected should send mail to all selected people', async (t) => {
+  const app = new Application();  
+  await new Promise(resolve => setTimeout(resolve, 10));
+  
+  app.selected = ['Alice', 'Bob'];
+  
+  const originalWrite = app.mailSystem.write;
+  const originalSend = app.mailSystem.send;
+  
+  const writeCalls = [];
+  const sendCalls = [];
+  
+  app.mailSystem.write = (name) => {
+    writeCalls.push(name);
+    return `Congrats, ${name}!`;
+  };
+  
+  app.mailSystem.send = (name, context) => {
+    sendCalls.push({ name, context });
+    return true;
+  };
+  
+  app.notifySelected();
+  
+  assert.strictEqual(writeCalls.length, 2);
+  assert.strictEqual(sendCalls.length, 2);
+  
+  assert.strictEqual(writeCalls[0], 'Alice');
+  assert.strictEqual(writeCalls[1], 'Bob');
+  
+  assert.strictEqual(sendCalls[0].name, 'Alice');
+  assert.strictEqual(sendCalls[0].context, 'Congrats, Alice!');
+  assert.strictEqual(sendCalls[1].name, 'Bob');
+  assert.strictEqual(sendCalls[1].context, 'Congrats, Bob!');
+  
+  app.mailSystem.write = originalWrite;
+  app.mailSystem.send = originalSend;
+});
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