How to test email sending with Mailhog on local? - testing

Question

Setup mailhog with docker-compose like:
version: '3'
services:
mailhog:
image: mailhog/mailhog
ports:
- 8025:8025
- 1025:1025
It's possible to access localhost:8025 from browser. Maybe the SMTP server 1025 also works but don't know how to confirm it.
In a NestJS application, for testing the email code as:
#Module({
imports: [NodeMailerModule],
providers: [MailHogEmailRepository],
exports: [MailHogEmailRepository],
})
class MailHogEmailRepositoryModule {}
#Module({
imports: [MailHogEmailRepositoryModule],
providers: [
{
provide: EmailRepository,
useFactory: (
config: ConfigService,
mailHog: MailHogEmailRepository,
) => {
return mailHog;
}
},
inject: [ConfigService, MailHogEmailRepository],
},
],
exports: [EmailRepository],
})
export class EmailRepositoryModule {}
MailHogEmailRepository send with nodemailer:
#Injectable()
export class MailHogEmailRepository implements EmailRepository {
constructor(
#Inject(NodeMailerToken) private readonly nodemailer: Transporter,
) {}
async send(email: Email) {
const options = {
to: email.to,
from: email.from,
subject: email.subject,
};
await this.nodemailer.sendMail(options);
}
}
nodemailer config:
import { Module } from '#nestjs/common';
import { ConfigService } from '#nestjs/config';
import { createTransport } from 'nodemailer';
export const NodeMailerToken = Symbol('nodemailer');
#Module({
providers: [
{
provide: NodeMailerToken,
useFactory: (config: ConfigService) =>
createTransport({
host: 'localhost',
port: 1025,
secure: true,
}),
inject: [ConfigService],
},
],
exports: [NodeMailerToken],
})
export class NodeMailerModule {}
In test source, it always timeout:
import { Test, TestingModule } from '#nestjs/testing';
import request from 'supertest';
import {
FastifyAdapter,
NestFastifyApplication,
} from '#nestjs/platform-fastify';
describe('Test sender', () => {
let app: NestFastifyApplication;
beforeEach(async () => {
const moduleFixture: TestingModule = await Test.createTestingModule({
imports: [AppModule],
}).compile();
app = moduleFixture.createNestApplication(new FastifyAdapter());
await app.init();
await app.getHttpAdapter().getInstance().ready();
});
describe('/handler (POST)', () => {
describe('should send data to mail server', () => {
it('success', () => {
const message = ...
return request(app.getHttpServer())
.post('/handler')
.send({ message })
.expect(200);
});
});
});
});
$ npm run test
thrown: "Exceeded timeout of xxx ms for a test.
Use jest.setTimeout(newTimeout) to increase the timeout value, if this is a long-running test."
It seems the test case couldn't access the mailhog server running in docker container. How to set it correctly?