Spring Boot Integration Testing

Table of Contents

1. Overview
2. About the application
   1. Database schema
3. Environment prerequisites
4. Build instructions
5. About integration testing
6. Instructions

1. Overview

This repository is intended to provide a sample Spring Boot project for those who wish to learn and practice integration testing. The main idea is to provide a “playground”, so that whoever makes use of this repository only focuses on implementing tests without worrying about developing the functionality of the application. Explanations will be provided on the importance of integration testing, as well as examples and proposed exercises to practice.

2. About the application

This sample project is a simple Spring Boot project emulating a music store. It exposes REST APIs to execute CRUD operations over resources like Artists, Albums and Songs.
It uses an in-memory database called H2, so you'll find pre-existing data examples.

Database schema

3. Environment prerequisites

1. Install JDK 21

4. Build instructions

1. Fork this repository
2. Once fork is complete, clone the repository.
3. Open the project with your favourite editor/IDE (Eclipse, VSCode, IntelliJ, etc.).
4. Open a new terminal, move to the project's location and execute the command .\gradlew clean build and wait for completion
5. Finally, execute the application using your editor/IDE or executing .\gradlew bootRun

If you want to verify application is running you can open the: Swagger documentation

You should see something like this:

Here, you'll find the resources to execute CRUD operations for Artists, Albums and Songs. For example, you can get the lists of artists:

1. In the artists section look for the GET API "Returns a paginated list of artists", click on it and then click on the Try it out option.

2. Then click on Execute option.

3. You should see a list of artists

5. About integration testing

Integration Testing is a form of testing focused in testing interactions between internal and external components, but not as a whole system or flow. Some examples of external components are databases, external services, files, etc. Unlike unit tests, integration tests don't simulate or mock interactions with external components, allowing to catch bugs that can't be caught with unit tests.

One disadvantage that integration tests have, is that they're more complicated to execute since previous configuration is needed in order to interact with the external components. They're slow and takes more time to execute them.

In this demo project will be focusing on writing integration tests to test the persistence layer (repositories) and presentation layer (controllers).

6. Instructions

As mentioned before, we'll focus on testing persistence and presentation layers. To write and execute the tests, we'll make use of a library called JUnit and we'll use an assertion library called AssertJ, Below you'll find a list of explanations and proposed exercises, please follow them in that order.

💡 IMPORTANT

We'll be working on the main branch but if you take a look, there's another branch called ending_branch this branch contains more implementation examples for the suggested exercises, you can use this branch to compare it with your tests in case you get stuck, but ideally you should try to solve the exercises by your own by making google searches and investigating so you can really develop an understanding of the subject.

Exercises

Testing persistence layer

1. Testing AlbumRepository
2. Testing ArtistRepository
3. Testing SongRepository

Testing persistence layer

1. Testing ArtistController
2. Testing AlbumnController - same instructions as ArtistController
3. Testing SongController - same instructions as ArtistController

7. Resources

Official Language/Framework/Library Documentation

• Testing Spring Boot Applications
• Testing the Web layer
• @DataJpaTest annotation

Blog articles, samples

• @SpringBootTest annotation
• Spring Boot Integration Testing
• Spring Boot @DataJpaTest

Video tutorials

• Spring Boot Testing
• How to Integration Test In Spring Boot
• Spring Boot Testcontainers - Integration Testing made easy!