Test database strategies in NestJS - Mini Project: Build & Apply

Test Database Strategies in NestJS

📖 Scenario: You are building a NestJS application that interacts with a database. To ensure your code works correctly, you want to write tests that use a test database setup.This project will guide you through creating a simple test database strategy using an in-memory database for testing your service.

🎯 Goal: Build a basic NestJS test setup that uses an in-memory test database to verify a service method.

📋 What You'll Learn

Create a test module with an in-memory database provider

Configure a test database connection variable

Write a test that queries the test database using the service

Complete the test setup with proper module imports and providers

💡 Why This Matters

🌍 Real World

Testing database interactions safely without affecting production data is essential in real-world applications.

💼 Career

Understanding test database strategies is important for backend developers working with NestJS or any server-side framework to ensure reliable and maintainable code.

1

Create the test database provider

Create a constant called testDatabaseProvider that provides an in-memory database connection string with the value 'sqlite::memory:'.

NestJS

# Your code here

Need a hint?

Use an object with provide and useValue keys to create the provider.

2

Configure the test database connection variable

Create a variable called testDbConnection and assign it the string 'sqlite::memory:' to represent the test database connection string.

NestJS

export const testDatabaseProvider = {
  provide: 'DATABASE_CONNECTION',
  useValue: 'sqlite::memory:',
};

# Your code here

Need a hint?

Just assign the string 'sqlite::memory:' to the variable testDbConnection.

3

Write a test that uses the test database

Write a Jest test function called it with the description 'should connect to test database' that expects testDbConnection to equal 'sqlite::memory:'.

NestJS

export const testDatabaseProvider = {
  provide: 'DATABASE_CONNECTION',
  useValue: 'sqlite::memory:',
};

const testDbConnection = 'sqlite::memory:';

# Your code here

Need a hint?

Use Jest's it function and expect to check the connection string.

4

Complete the test module setup

Create a NestJS test module using Test.createTestingModule that imports an empty array, provides testDatabaseProvider, and compile it. Assign the compiled module to a constant called module.

NestJS

export const testDatabaseProvider = {
  provide: 'DATABASE_CONNECTION',
  useValue: 'sqlite::memory:',
};

const testDbConnection = 'sqlite::memory:';

it('should connect to test database', () => {
  expect(testDbConnection).toBe('sqlite::memory:');
});

# Your code here

Need a hint?

Use await Test.createTestingModule({ imports: [], providers: [testDatabaseProvider] }).compile() and assign it to module.