add DNS service test

src/dns/dns.service.spec.ts

@@ -1,8 +1,14 @@
 import { Test, TestingModule } from '@nestjs/testing';
 import { DnsService } from './dns.service';
+import * as dns from 'dns';
+
+jest.mock('dns', () => ({
+  lookup: jest.fn(),
+}));
 
 describe('DnsService', () => {
   let service: DnsService;
+  let dnsLookupMock: jest.Mock;
 
   beforeEach(async () => {
     const module: TestingModule = await Test.createTestingModule({
@@ -10,9 +16,20 @@ describe('DnsService', () => {
     }).compile();
 
     service = module.get<DnsService>(DnsService);
+    dnsLookupMock = (dns.lookup as unknown) as jest.Mock;
   });
 
   it('should be defined', () => {
     expect(service).toBeDefined();
   });
+
+  it('should return true for a valid URL', async () => {
+    dnsLookupMock.mockImplementation((hostname, callback) => callback(null, '1.1.1.1'));
+    expect(await service.isValidUrl('http://example.com')).toBe(true);
+  });
+
+  it('should return false for an invalid URL', async () => {
+    dnsLookupMock.mockImplementation((hostname, callback) => callback(new Error('not found'), null));
+    expect(await service.isValidUrl('http://invalid-url.com')).toBe(false);
+  });
 });

src/dns/dns.service.ts

@@ -7,7 +7,6 @@ export class DnsService {
   private lookup = util.promisify(dns.lookup);
 
   async isValidUrl(url: string): Promise<boolean> {
-    console.log(url)
     try {
       const hostname = new URL(url).hostname;
       await this.lookup(hostname);