Testing module setup in NestJS - Mini Project: Build & Apply

Testing Module Setup in NestJS

📖 Scenario: You are building a simple NestJS service that manages a list of books. To ensure your service works correctly, you want to set up a testing module using NestJS's testing utilities.This project guides you step-by-step to create a testing module, configure it, and write a basic test setup.

🎯 Goal: Build a NestJS testing module setup for a BooksService that can be used to write unit tests.

📋 What You'll Learn

Create a testing module with Test.createTestingModule

Provide the BooksService in the testing module

Compile the testing module

Retrieve the BooksService instance from the testing module

💡 Why This Matters

🌍 Real World

Setting up a testing module is essential in NestJS projects to isolate and test services and controllers without running the full application.

💼 Career

Understanding how to configure and use NestJS testing modules is a key skill for backend developers working with NestJS to ensure code quality and reliability.

1

Create a Testing Module

Import Test from @nestjs/testing and create a testing module using Test.createTestingModule with a providers array containing BooksService.

NestJS

import { BooksService } from './books.service';
// Create a testing module with BooksService as provider
// Your code here

Need a hint?

Use Test.createTestingModule and pass an object with providers array including BooksService. Then call .compile() to build the module.

2

Add a Variable for BooksService

Declare a variable called booksService to hold the instance of BooksService retrieved from the testing module.

NestJS

import { Test } from '@nestjs/testing';
import { BooksService } from './books.service';

const moduleRef = await Test.createTestingModule({
  providers: [BooksService],
}).compile();

// Declare booksService variable
// Your code here

Need a hint?

Declare booksService with type BooksService using let so you can assign it later.

3

Retrieve BooksService Instance

Assign the booksService variable by getting the BooksService instance from moduleRef using moduleRef.get(BooksService).

NestJS

import { Test } from '@nestjs/testing';
import { BooksService } from './books.service';

const moduleRef = await Test.createTestingModule({
  providers: [BooksService],
}).compile();

let booksService: BooksService;

// Assign booksService from moduleRef
// Your code here

Need a hint?

Use moduleRef.get(BooksService) to get the service instance and assign it to booksService.

4

Export the Testing Setup

Export the booksService variable so it can be used in test files.

NestJS

import { Test } from '@nestjs/testing';
import { BooksService } from './books.service';

const moduleRef = await Test.createTestingModule({
  providers: [BooksService],
}).compile();

let booksService: BooksService;

booksService = moduleRef.get(BooksService);

// Export booksService
// Your code here

Need a hint?

Use export { booksService } to make the variable available outside this module.