- 1. API with NestJS #1. Controllers, routing and the module structure
- 2. API with NestJS #2. Setting up a PostgreSQL database with TypeORM
- 3. API with NestJS #3. Authenticating users with bcrypt, Passport, JWT, and cookies
- 4. API with NestJS #4. Error handling and data validation
- 5. API with NestJS #5. Serializing the response with interceptors
- 6. API with NestJS #6. Looking into dependency injection and modules
- 7. API with NestJS #7. Creating relationships with Postgres and TypeORM
- 8. API with NestJS #8. Writing unit tests
- 9. API with NestJS #9. Testing services and controllers with integration tests
- 10. API with NestJS #10. Uploading public files to Amazon S3
- 11. API with NestJS #11. Managing private files with Amazon S3
- 12. API with NestJS #12. Introduction to Elasticsearch
- 13. API with NestJS #13. Implementing refresh tokens using JWT
- 14. API with NestJS #14. Improving performance of our Postgres database with indexes
- 15. API with NestJS #15. Defining transactions with PostgreSQL and TypeORM
- 16. API with NestJS #16. Using the array data type with PostgreSQL and TypeORM
- 17. API with NestJS #17. Offset and keyset pagination with PostgreSQL and TypeORM
- 18. API with NestJS #18. Exploring the idea of microservices
- 19. API with NestJS #19. Using RabbitMQ to communicate with microservices
- 20. API with NestJS #20. Communicating with microservices using the gRPC framework
- 21. API with NestJS #21. An introduction to CQRS
- 22. API with NestJS #22. Storing JSON with PostgreSQL and TypeORM
- 23. API with NestJS #23. Implementing in-memory cache to increase the performance
- 24. API with NestJS #24. Cache with Redis. Running the app in a Node.js cluster
- 25. API with NestJS #25. Sending scheduled emails with cron and Nodemailer
- 26. API with NestJS #26. Real-time chat with WebSockets
- 27. API with NestJS #27. Introduction to GraphQL. Queries, mutations, and authentication
- 28. API with NestJS #28. Dealing in the N + 1 problem in GraphQL
- 29. API with NestJS #29. Real-time updates with GraphQL subscriptions
- 30. API with NestJS #30. Scalar types in GraphQL
- 31. API with NestJS #31. Two-factor authentication
- 32. API with NestJS #32. Introduction to Prisma with PostgreSQL
- 33. API with NestJS #33. Managing PostgreSQL relationships with Prisma
- 34. API with NestJS #34. Handling CPU-intensive tasks with queues
- 35. API with NestJS #35. Using server-side sessions instead of JSON Web Tokens
- 36. API with NestJS #36. Introduction to Stripe with React
- 37. API with NestJS #37. Using Stripe to save credit cards for future use
- 38. API with NestJS #38. Setting up recurring payments via subscriptions with Stripe
- 39. API with NestJS #39. Reacting to Stripe events with webhooks
- 40. API with NestJS #40. Confirming the email address
- 41. API with NestJS #41. Verifying phone numbers and sending SMS messages with Twilio
- 42. API with NestJS #42. Authenticating users with Google
- 43. API with NestJS #43. Introduction to MongoDB
- 44. API with NestJS #44. Implementing relationships with MongoDB
- 45. API with NestJS #45. Virtual properties with MongoDB and Mongoose
- 46. API with NestJS #46. Managing transactions with MongoDB and Mongoose
- 47. API with NestJS #47. Implementing pagination with MongoDB and Mongoose
- 48. API with NestJS #48. Definining indexes with MongoDB and Mongoose
- 49. API with NestJS #49. Updating with PUT and PATCH with MongoDB and Mongoose
- 50. API with NestJS #50. Introduction to logging with the built-in logger and TypeORM
- 51. API with NestJS #51. Health checks with Terminus and Datadog
- 52. API with NestJS #52. Generating documentation with Compodoc and JSDoc
- 53. API with NestJS #53. Implementing soft deletes with PostgreSQL and TypeORM
- 54. API with NestJS #54. Storing files inside a PostgreSQL database
- 55. API with NestJS #55. Uploading files to the server
- 56. API with NestJS #56. Authorization with roles and claims
- 57. API with NestJS #57. Composing classes with the mixin pattern
- 58. API with NestJS #58. Using ETag to implement cache and save bandwidth
- 59. API with NestJS #59. Introduction to a monorepo with Lerna and Yarn workspaces
- 60. API with NestJS #60. The OpenAPI specification and Swagger
- 61. API with NestJS #61. Dealing with circular dependencies
- 62. API with NestJS #62. Introduction to MikroORM with PostgreSQL
- 63. API with NestJS #63. Relationships with PostgreSQL and MikroORM
- 64. API with NestJS #64. Transactions with PostgreSQL and MikroORM
- 65. API with NestJS #65. Implementing soft deletes using MikroORM and filters
- 66. API with NestJS #66. Improving PostgreSQL performance with indexes using MikroORM
- 67. API with NestJS #67. Migrating to TypeORM 0.3
- 68. API with NestJS #68. Interacting with the application through REPL
- 69. API with NestJS #69. Database migrations with TypeORM
- 70. API with NestJS #70. Defining dynamic modules
- 71. API with NestJS #71. Introduction to feature flags
- 72. API with NestJS #72. Working with PostgreSQL using raw SQL queries
- 73. API with NestJS #73. One-to-one relationships with raw SQL queries
- 74. API with NestJS #74. Designing many-to-one relationships using raw SQL queries
- 75. API with NestJS #75. Many-to-many relationships using raw SQL queries
- 76. API with NestJS #76. Working with transactions using raw SQL queries
- 77. API with NestJS #77. Offset and keyset pagination with raw SQL queries
- 78. API with NestJS #78. Generating statistics using aggregate functions in raw SQL
- 79. API with NestJS #79. Implementing searching with pattern matching and raw SQL
- 80. API with NestJS #80. Updating entities with PUT and PATCH using raw SQL queries
- 81. API with NestJS #81. Soft deletes with raw SQL queries
- 82. API with NestJS #82. Introduction to indexes with raw SQL queries
- 83. API with NestJS #83. Text search with tsvector and raw SQL
- 84. API with NestJS #84. Implementing filtering using subqueries with raw SQL
- 85. API with NestJS #85. Defining constraints with raw SQL
- 86. API with NestJS #86. Logging with the built-in logger when using raw SQL
- 87. API with NestJS #87. Writing unit tests in a project with raw SQL
- 88. API with NestJS #88. Testing a project with raw SQL using integration tests
- 89. API with NestJS #89. Replacing Express with Fastify
- 90. API with NestJS #90. Using various types of SQL joins
- 91. API with NestJS #91. Dockerizing a NestJS API with Docker Compose
- 92. API with NestJS #92. Increasing the developer experience with Docker Compose
- 93. API with NestJS #93. Deploying a NestJS app with Amazon ECS and RDS
- 94. API with NestJS #94. Deploying multiple instances on AWS with a load balancer
- 95. API with NestJS #95. CI/CD with Amazon ECS and GitHub Actions
- 96. API with NestJS #96. Running unit tests with CI/CD and GitHub Actions
- 97. API with NestJS #97. Introduction to managing logs with Amazon CloudWatch
- 98. API with NestJS #98. Health checks with Terminus and Amazon ECS
- 99. API with NestJS #99. Scaling the number of application instances with Amazon ECS
- 100. API with NestJS #100. The HTTPS protocol with Route 53 and AWS Certificate Manager
- 101. API with NestJS #101. Managing sensitive data using the AWS Secrets Manager
- 102. API with NestJS #102. Writing unit tests with Prisma
- 103. API with NestJS #103. Integration tests with Prisma
- 104. API with NestJS #104. Writing transactions with Prisma
- 105. API with NestJS #105. Implementing soft deletes with Prisma and middleware
- 106. API with NestJS #106. Improving performance through indexes with Prisma
- 107. API with NestJS #107. Offset and keyset pagination with Prisma
- 108. API with NestJS #108. Date and time with Prisma and PostgreSQL
- 109. API with NestJS #109. Arrays with PostgreSQL and Prisma
- 110. API with NestJS #110. Managing JSON data with PostgreSQL and Prisma
- 111. API with NestJS #111. Constraints with PostgreSQL and Prisma
- 112. API with NestJS #112. Serializing the response with Prisma
- 113. API with NestJS #113. Logging with Prisma
- 114. API with NestJS #114. Modifying data using PUT and PATCH methods with Prisma
- 115. API with NestJS #115. Database migrations with Prisma
- 116. API with NestJS #116. REST API versioning
- 117. API with NestJS #117. CORS – Cross-Origin Resource Sharing
- 118. API with NestJS #118. Uploading and streaming videos
- 119. API with NestJS #119. Type-safe SQL queries with Kysely and PostgreSQL
- 120. API with NestJS #120. One-to-one relationships with the Kysely query builder
- 121. API with NestJS #121. Many-to-one relationships with PostgreSQL and Kysely
- 122. API with NestJS #122. Many-to-many relationships with Kysely and PostgreSQL
- 123. API with NestJS #123. SQL transactions with Kysely
- 124. API with NestJS #124. Handling SQL constraints with Kysely
- 125. API with NestJS #125. Offset and keyset pagination with Kysely
- 126. API with NestJS #126. Improving the database performance with indexes and Kysely
- 127. API with NestJS #127. Arrays with PostgreSQL and Kysely
- 128. API with NestJS #128. Managing JSON data with PostgreSQL and Kysely
- 129. API with NestJS #129. Implementing soft deletes with SQL and Kysely
- 130. API with NestJS #130. Avoiding storing sensitive information in API logs
- 131. API with NestJS #131. Unit tests with PostgreSQL and Kysely
- 132. API with NestJS #132. Handling date and time in PostgreSQL with Kysely
- 133. API with NestJS #133. Introducing database normalization with PostgreSQL and Prisma
- 134. API with NestJS #134. Aggregating statistics with PostgreSQL and Prisma
- 135. API with NestJS #135. Referential actions and foreign keys in PostgreSQL with Prisma
- 136. API with NestJS #136. Raw SQL queries with Prisma and PostgreSQL range types
- 137. API with NestJS #137. Recursive relationships with Prisma and PostgreSQL
- 138. API with NestJS #138. Filtering records with Prisma
- 139. API with NestJS #139. Using UUID as primary keys with Prisma and PostgreSQL
- 140. API with NestJS #140. Using multiple PostgreSQL schemas with Prisma
- 141. API with NestJS #141. Getting distinct records with Prisma and PostgreSQL
- 142. API with NestJS #142. A video chat with WebRTC and React
- 143. API with NestJS #143. Optimizing queries with views using PostgreSQL and Kysely
- 144. API with NestJS #144. Creating CLI applications with the Nest Commander
- 145. API with NestJS #145. Securing applications with Helmet
- 146. API with NestJS #146. Polymorphic associations with PostgreSQL and Prisma
- 147. API with NestJS #147. The data types to store money with PostgreSQL and Prisma
- 148. API with NestJS #148. Understanding the injection scopes
- 149. API with NestJS #149. Introduction to the Drizzle ORM with PostgreSQL
- 150. API with NestJS #150. One-to-one relationships with the Drizzle ORM
- 151. API with NestJS #151. Implementing many-to-one relationships with Drizzle ORM
- 152. API with NestJS #152. SQL constraints with the Drizzle ORM
- 153. API with NestJS #153. SQL transactions with the Drizzle ORM
- 154. API with NestJS #154. Many-to-many relationships with Drizzle ORM and PostgreSQL
- 155. API with NestJS #155. Offset and keyset pagination with the Drizzle ORM
- 156. API with NestJS #156. Arrays with PostgreSQL and the Drizzle ORM
- 157. API with NestJS #157. Handling JSON data with PostgreSQL and the Drizzle ORM
- 158. API with NestJS #158. Soft deletes with the Drizzle ORM
- 159. API with NestJS #159. Date and time with PostgreSQL and the Drizzle ORM
- 160. API with NestJS #160. Using views with the Drizzle ORM and PostgreSQL
- 161. API with NestJS #161. Generated columns with the Drizzle ORM and PostgreSQL
- 162. API with NestJS #162. Identity columns with the Drizzle ORM and PostgreSQL
- 163. API with NestJS #163. Full-text search with the Drizzle ORM and PostgreSQL
- 164. API with NestJS #164. Improving the performance with indexes using Drizzle ORM
- 165. API with NestJS #165. Time intervals with the Drizzle ORM and PostgreSQL
- 166. API with NestJS #166. Logging with the Drizzle ORM
- 167. API with NestJS #167. Unit tests with the Drizzle ORM
- 168. API with NestJS #168. Integration tests with the Drizzle ORM
- 169. API with NestJS #169. Unique IDs with UUIDs using Drizzle ORM and PostgreSQL
- 170. API with NestJS #170. Polymorphic associations with PostgreSQL and Drizzle ORM
- 171. API with NestJS #171. Recursive relationships with Drizzle ORM and PostgreSQL
- 172. API with NestJS #172. Database normalization with Drizzle ORM and PostgreSQL
- 173. API with NestJS #173. Storing money with Drizzle ORM and PostgreSQL
- 174. API with NestJS #174. Multiple PostgreSQL schemas with Drizzle ORM
- 175. API with NestJS #175. PUT and PATCH requests with PostgreSQL and Drizzle ORM
- 176. API with NestJS #176. Database migrations with the Drizzle ORM
- 177. API with NestJS #177. Response serialization with the Drizzle ORM
- 178. API with NestJS #178. Storing files inside of a PostgreSQL database with Drizzle
- 179. API with NestJS #179. Pattern matching search with Drizzle ORM and PostgreSQL
- 180. API with NestJS #180. Organizing Drizzle ORM schema with PostgreSQL
Creating tests is essential when trying to build a robust and dependable application. In this article, we clarify the concept of unit tests and demonstrate how to write them for our application that interacts with PostgreSQL and uses the Kysely library.
Explaining unit tests
A unit test ensures that a specific part of our code operates correctly. Using these tests, we can confirm that different sections of our system function properly on their own. Each unit test should be independent and isolated.
When we execute the npm run test command, Jest searches for files following a particular naming pattern. When we use NestJS, it looks for files that end with .spec.ts by default. Another common practice is to use files with the .test.ts extension. You can find this configuration in our package.json file.
package.json
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{ // ... "jest": { "testRegex": ".*\\.(spec|test)\\.ts$", // ... } } |
Let’s start by creating a simple test for our AuthenticationService class.
authentication.service.test.ts
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import { AuthenticationService } from './authentication.service'; import { JwtService } from '@nestjs/jwt'; import { ConfigService } from '@nestjs/config'; import { Pool } from 'pg'; import { UsersService } from '../users/users.service'; import { UsersRepository } from '../users/users.repository'; import { Database } from '../database/database'; import { PostgresDialect } from 'kysely'; describe('The AuthenticationService', () => { let authenticationService: AuthenticationService; beforeEach(() => { const configService = new ConfigService(); authenticationService = new AuthenticationService( new UsersService( new UsersRepository( new Database({ dialect: new PostgresDialect({ pool: new Pool({ host: configService.get('POSTGRES_HOST'), port: configService.get('POSTGRES_PORT'), user: configService.get('POSTGRES_USER'), password: configService.get('POSTGRES_PASSWORD'), database: configService.get('POSTGRES_DB'), }), }), }), ), ), new JwtService({ secretOrPrivateKey: 'Secret key', }), new ConfigService(), ); }); describe('when calling the getCookieForLogOut method', () => { it('should return a correct string', () => { const result = authenticationService.getCookieForLogOut(); expect(result).toBe('Authentication=; HttpOnly; Path=/; Max-Age=0'); }); }); }); |
PASS src/authentication/authentication.service.test.ts
The AuthenticationService
when calling the getCookieForLogOut method
✓ should return a correct string
In the example above, we’re calling the AuthenticationService constructor manually. While this is one of the possible solutions, we can rely on NestJS test utilities to handle it for us instead. To do that, we need the Test.createTestingModule method from the @nestjs/testing library.
authentication.service.test.ts
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import { AuthenticationService } from './authentication.service'; import { JwtModule } from '@nestjs/jwt'; import { ConfigModule, ConfigService } from '@nestjs/config'; import { DatabaseModule } from '../database/database.module'; import { UsersModule } from '../users/users.module'; import { Test } from '@nestjs/testing'; import { EnvironmentVariables } from '../types/environmentVariables'; describe('The AuthenticationService', () => { let authenticationService: AuthenticationService; beforeEach(async () => { const module = await Test.createTestingModule({ providers: [AuthenticationService], imports: [ UsersModule, ConfigModule.forRoot(), JwtModule.register({ secretOrPrivateKey: 'Secret key', }), DatabaseModule.forRootAsync({ imports: [ConfigModule], inject: [ConfigService], useFactory: ( configService: ConfigService<EnvironmentVariables, true>, ) => ({ host: configService.get('POSTGRES_HOST'), port: configService.get('POSTGRES_PORT'), user: configService.get('POSTGRES_USER'), password: configService.get('POSTGRES_PASSWORD'), database: configService.get('POSTGRES_DB'), }), }), ], }).compile(); authenticationService = await module.get(AuthenticationService); }); describe('when calling the getCookieForLogOut method', () => { it('should return a correct string', () => { const result = authenticationService.getCookieForLogOut(); expect(result).toBe('Authentication=; HttpOnly; Path=/; Max-Age=0'); }); }); }); |
Above, we create a mock of the entire NestJS runtime. Then, when we execute the compile() method, we set up the module with its dependencies in a manner similar to how the bootstrap function in our main.ts file functions.
Avoiding connecting to the actual database
The above code has a significant issue, unfortunately. Our DatabaseModule class connects to a real PostgreSQL database. For unit tests to be independent and reliable, we should avoid that.
Removing the DatabaseModule from our imports causes an issue, though.
Error: Nest can’t resolve dependencies of the UsersRepository (?). Please make sure that the argument Database at index [0] is available in the UsersModule context.
To solve this problem, we need to notice that the UsersService class uses the database under the hood. We can avoid that by providing a mocked version of the UsersService.
It might make sense to refrain from mocking entire modules when writing unit tests. By doing that we would avoid testing how modules and classes interact with each other and test the parts of our system in isolation.
authentication.service.test.ts
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import { AuthenticationService } from './authentication.service'; import { JwtModule } from '@nestjs/jwt'; import { ConfigModule } from '@nestjs/config'; import { Test } from '@nestjs/testing'; import { SignUpDto } from './dto/signUp.dto'; import { UsersService } from '../users/users.service'; describe('The AuthenticationService', () => { let signUpData: SignUpDto; let authenticationService: AuthenticationService; beforeEach(async () => { signUpData = { email: 'john@smith.com', name: 'John', password: 'strongPassword123', }; const module = await Test.createTestingModule({ providers: [ AuthenticationService, { provide: UsersService, useValue: { create: jest.fn().mockReturnValue(signUpData), }, }, ], imports: [ ConfigModule.forRoot(), JwtModule.register({ secretOrPrivateKey: 'Secret key', }), ], }).compile(); authenticationService = await module.get(AuthenticationService); }); describe('when calling the getCookieForLogOut method', () => { it('should return a correct string', () => { const result = authenticationService.getCookieForLogOut(); expect(result).toBe('Authentication=; HttpOnly; Path=/; Max-Age=0'); }); }); describe('when registering a new user', () => { describe('and when the usersService returns the new user', () => { it('should return the new user', async () => { const result = await authenticationService.signUp(signUpData); expect(result).toBe(signUpData); }); }); }); }); |
PASS src/authentication/authentication.service.test.ts
The AuthenticationService
when calling the getCookieForLogOut method
✓ should return a correct string
when registering a new user
and when the usersService returns the new user
✓ should return the new user
Mocking the UsersService class gives us the confidence that our tests won’t use the actual database.
Changing the mock per test
In the test above, we mock the getByEmail method always to return a valid user. However, that’s not always true:
- when we type the email of an existing user in our database, the method returns the user.
- if the user with that specific email doesn’t exist, it throws the NotFoundException.
Let’s create a mock that covers both cases.
authentication.service.test.ts
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import { AuthenticationService } from './authentication.service'; import { JwtModule } from '@nestjs/jwt'; import { ConfigModule } from '@nestjs/config'; import { Test } from '@nestjs/testing'; import { SignUpDto } from './dto/signUp.dto'; import { UsersService } from '../users/users.service'; import { User } from '../users/user.model'; import * as bcrypt from 'bcrypt'; import { BadRequestException, NotFoundException } from '@nestjs/common'; describe('The AuthenticationService', () => { let signUpData: SignUpDto; let authenticationService: AuthenticationService; let getByEmailMock: jest.Mock; let password: string; beforeEach(async () => { getByEmailMock = jest.fn(); password = 'strongPassword123'; signUpData = { password, email: 'john@smith.com', name: 'John', }; const module = await Test.createTestingModule({ providers: [ AuthenticationService, { provide: UsersService, useValue: { create: jest.fn().mockReturnValue(signUpData), getByEmail: getByEmailMock, }, }, ], imports: [ ConfigModule.forRoot(), JwtModule.register({ secretOrPrivateKey: 'Secret key', }), ], }).compile(); authenticationService = await module.get(AuthenticationService); }); describe('when calling the getCookieForLogOut method', () => { // ... }); describe('when registering a new user', () => { // ... }); describe('when the getAuthenticatedUser method is called', () => { describe('and a valid email and password are provided', () => { let userData: User; beforeEach(async () => { const hashedPassword = await bcrypt.hash(password, 10); userData = { id: 1, email: 'john@smith.com', name: 'John', password: hashedPassword, }; getByEmailMock.mockResolvedValue(userData); // 👈 }); it('should return the new user', async () => { const result = await authenticationService.getAuthenticatedUser( userData.email, password, ); expect(result).toBe(userData); }); }); describe('and an invalid email is provided', () => { beforeEach(() => { getByEmailMock.mockRejectedValue(new NotFoundException()); // 👈 }); it('should throw the BadRequestException', () => { return expect(async () => { await authenticationService.getAuthenticatedUser( 'john@smith.com', password, ); }).rejects.toThrow(BadRequestException); }); }); }); }); |
The AuthenticationService
when calling the getCookieForLogOut method
✓ should return a correct string
when registering a new user
and when the usersService returns the new user
✓ should return the new userwhen the getAuthenticatedUser method is called
and a valid email and password are provided
✓ should return the new user
and an invalid email is provided
✓ should throw the BadRequestException
Above, we create the getByEmailMock variable and use it in the mocked UsersService. Then, we use the getByEmailMock.mockResolvedValue method to change the value returned by the getByEmail method.
An important thing to notice is that we are focusing on testing the logic contained in the methods of the AuthenticationService while making sure that the tests don’t rely on the code of the UsersService.
Mocking Kysely
So far, we haven’t tested a class that uses Kysely directly. Let’s take a look at the create method in the UsersRepository.
users.repository.ts
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import { BadRequestException, Injectable } from '@nestjs/common'; import { User } from './user.model'; import { CreateUserDto } from './dto/createUser.dto'; import { Database } from '../database/database'; import { isDatabaseError } from '../types/databaseError'; import { PostgresErrorCode } from '../database/postgresErrorCode.enum'; @Injectable() export class UsersRepository { constructor(private readonly database: Database) {} async create(userData: CreateUserDto) { try { const databaseResponse = await this.database .insertInto('users') .values({ password: userData.password, email: userData.email, name: userData.name, }) .returningAll() .executeTakeFirstOrThrow(); return new User(databaseResponse); } catch (error) { if ( isDatabaseError(error) && error.code === PostgresErrorCode.UniqueViolation ) { throw new BadRequestException('User with this email already exists'); } throw error; } } // ... } |
Above, we can see two cases:
- if the database manages to create a new row in the table, the create method returns an instance of the User class,
- if Kysely throws an error because the user with a particular email already exists, the create method throws the BadRequestException.
To test both situations, we need to mock Kysely. A very important thing to notice is that we are chaining the insertInto, values, and returningAll methods. Because of that, they all should return an instance of Kysely. To achieve that, we can use jest.fn().mockReturnThis().
users.repository.test.ts
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import { CreateUserDto } from './dto/createUser.dto'; import { Test } from '@nestjs/testing'; import { UsersRepository } from './users.repository'; import { Database } from '../database/database'; describe('The UsersRepository class', () => { let executeTakeFirstOrThrowMock: jest.Mock; let createUserData: CreateUserDto; let usersRepository: UsersRepository; beforeEach(async () => { createUserData = { name: 'John', email: 'john@smith.com', password: 'strongPassword123', }; executeTakeFirstOrThrowMock = jest.fn(); const module = await Test.createTestingModule({ providers: [ UsersRepository, { provide: Database, useValue: { insertInto: jest.fn().mockReturnThis(), values: jest.fn().mockReturnThis(), returningAll: jest.fn().mockReturnThis(), executeTakeFirstOrThrow: executeTakeFirstOrThrowMock, }, }, ], }).compile(); usersRepository = await module.get(UsersRepository); }); // ... }); |
Please notice that we are not using jest.fn().mockReturnThis() for the executeTakeFirstOrThrow method. Instead, we will change this mock based on the test case.
users.repository.test.ts
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import { CreateUserDto } from './dto/createUser.dto'; import { Test } from '@nestjs/testing'; import { UsersRepository } from './users.repository'; import { User, UserModelData } from './user.model'; import { DatabaseError } from '../types/databaseError'; import { PostgresErrorCode } from '../database/postgresErrorCode.enum'; import { Database } from '../database/database'; import { BadRequestException } from '@nestjs/common'; describe('The UsersRepository class', () => { let executeTakeFirstOrThrowMock: jest.Mock; let createUserData: CreateUserDto; let usersRepository: UsersRepository; beforeEach(async () => { createUserData = { name: 'John', email: 'john@smith.com', password: 'strongPassword123', }; executeTakeFirstOrThrowMock = jest.fn(); const module = await Test.createTestingModule({ providers: [ UsersRepository, { provide: Database, useValue: { insertInto: jest.fn().mockReturnThis(), values: jest.fn().mockReturnThis(), returningAll: jest.fn().mockReturnThis(), executeTakeFirstOrThrow: executeTakeFirstOrThrowMock, }, }, ], }).compile(); usersRepository = await module.get(UsersRepository); }); describe('when the create method is called', () => { describe('and the database returns valid data', () => { let userModelData: UserModelData; beforeEach(() => { userModelData = { id: 1, name: 'John', email: 'john@smith.com', password: 'strongPassword123', address_id: null, address_street: null, address_city: null, address_country: null, }; executeTakeFirstOrThrowMock.mockResolvedValue(userModelData); }); it('should return an instance of the UserModel', async () => { const result = await usersRepository.create(createUserData); expect(result instanceof User).toBe(true); }); it('should return the UserModel with correct properties', async () => { const result = await usersRepository.create(createUserData); expect(result.id).toBe(userModelData.id); expect(result.email).toBe(userModelData.email); expect(result.name).toBe(userModelData.name); expect(result.password).toBe(userModelData.password); expect(result.address).not.toBeDefined(); }); }); describe('and the database throws the UniqueViolation', () => { beforeEach(() => { const databaseError: DatabaseError = { code: PostgresErrorCode.UniqueViolation, table: 'users', detail: 'Key (email)=(john@smith.com) already exists.', }; executeTakeFirstOrThrowMock.mockImplementation(() => { throw databaseError; }); }); it('should throw the BadRequestException exception', () => { return expect(() => usersRepository.create(createUserData), ).rejects.toThrow(BadRequestException); }); }); }); }); |
PASS src/users/users.repository.test.ts
The UsersRepository class
when the create method is called
and the database returns valid data
✓ should return an instance of the UserModel
✓ should return the UserModel with correct properties
and the database throws the UniqueViolation
✓ should throw the BadRequestException exception
Above, we test both cases by setting the mocked executeTakeFirstOrThrow method to either return the user data or throw an error.
Summary
In this article, we’ve explained the concept of unit tests and their implementation in the context of NestJS. Our primary focus has been on testing the components of our application that interact with the database. Since unit tests should avoid using a real database connection, we’ve explored the technique of mocking our services and repositories. We also learned how to mock the Kysely library. All of the above serves as a good starting point for testing a NestJS project that uses SQL and Kysely.
can you make a blog about how to develop an abstract repository to decouple the data layer and the service layer .if the blog is in Typeorm and Postgres that will be better
Do you have a repo of this? I’m struggling reproducing the part where we mock Kysely, my service is still complaining for missing dep (Database) and I’d like too see the missing parts, especially how Database is defined.
Thx!
Sure thing. There you go:
https://github.com/mwanago/nestjs-kysely
It also has branches such as
part-143
orpart-131
if you want to see the code from a particular part of this series.