Testing Spring Boot Applications Demystified

This repository contains the source code for the book Testing Spring Boot Applications Demystified.

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Testing Spring Boot Applications Demystified

Requirements

Before you begin, ensure you have the following installed:

• Java 21
  • You can use SDKMAN! to install Java: sdk install java 21.0.6-tem
  • The project includes a .sdkmanrc file for automatic version switching
• Maven 3.6+ (wrapper included in the project)
• Docker (for running PostgreSQL via Docker Compose and Testcontainers during tests)
• Git (for cloning the repository)

Technologies Used

This project demonstrates testing techniques for a Spring Boot application that includes:

• Spring Boot 3 with Java 21
• Spring Data JPA with PostgreSQL
• Spring Security for authentication and authorization
• Spring WebFlux for reactive HTTP clients
• Thymeleaf for server-side templating
• Flyway for database migrations
• Testcontainers for integration testing
• WireMock for HTTP client mocking
• JUnit 5 as the testing framework
• AssertJ for fluent assertions

Building the Application

The project uses Maven as the build tool. You can use the Maven wrapper included in the project:

Compile the project

./mvnw compile

Build the application (skip tests)

./mvnw package -DskipTests

Build the application (with tests)

./mvnw verify

Running the Application

Using Docker Compose

The project includes Spring Boot Docker Compose support. Simply start the application, and Docker Compose will automatically start the PostgreSQL database:

./mvnw spring-boot:run

The PostgreSQL database will be started automatically using the configuration from compose.yml.

Manual Database Setup

Alternatively, you can start PostgreSQL manually using Docker Compose:

docker compose up -d

Then run the application:

./mvnw spring-boot:run

Running Tests

The project includes comprehensive test coverage with both unit and integration tests.

Run all tests

./mvnw verify

Run only unit tests

./mvnw test

Run only integration tests

./mvnw failsafe:integration-test

Test Configuration

• Unit Tests: Use Surefire plugin with parallel execution enabled
• Integration Tests: Use Failsafe plugin and follow the naming convention *IT.java or *WT.java
• Testcontainers: Automatically starts PostgreSQL containers for integration tests
• Context Caching: Examples included to optimize Spring context reuse across tests

Code Quality

The project enforces code quality standards:

• Spotless: Ensures consistent code formatting using Google Java Format

  ./mvnw spotless:check
  ./mvnw spotless:apply

• SortPOM: Keeps the pom.xml organized

  ./mvnw sortpom:verify

• Maven Enforcer: Validates dependency convergence

Key Testing Patterns Demonstrated

This codebase showcases various testing patterns covered in the book:

• Unit testing with JUnit 5 and Mockito
• Integration testing with @SpringBootTest
• Testing Spring Data JPA repositories
• Testing REST controllers with MockMvc
• Testing reactive WebClient with WireMock
• Spring Security testing techniques
• Optimizing Spring context caching
• Parallel test execution
• Testcontainers for realistic integration tests

License

The code in this repository is available for educational purposes as companion material for the book.

Testing is a team sport, so feel free to share the link to get the eBook copy of Testing Spring Boot Applications Demystified with your colleagues.

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Joyful Testing!