Why testing matters in Spring Boot - See It in Action

Why Testing Matters in Spring Boot

📖 Scenario: You are building a simple Spring Boot application that manages a list of books. To ensure your application works correctly and to avoid future bugs, you will add tests. Testing helps catch mistakes early and makes your code more reliable.

🎯 Goal: Build a Spring Boot project with a simple BookService class and write a test to check if the service returns the correct number of books.

📋 What You'll Learn

Create a BookService class with a method getBooks() that returns a list of book titles.

Add a configuration variable expectedBookCount to hold the expected number of books.

Write a test method in BookServiceTest that checks if getBooks() returns the expected number of books.

Use Spring Boot testing annotations to run the test.

💡 Why This Matters

🌍 Real World

Testing is essential in real projects to ensure your code works as expected and to prevent bugs from reaching users.

💼 Career

Knowing how to write and run tests in Spring Boot is a key skill for backend developers and improves code quality and maintainability.

1

Create the BookService class with a list of books

Create a class called BookService with a method getBooks() that returns a list containing exactly these three book titles: "Spring Basics", "Java Fundamentals", and "Testing Essentials".

Spring Boot

// Your code here

Need a hint?

Use List.of() to create a fixed list of book titles.

2

Add expectedBookCount variable

Inside the BookService class, add a private integer variable called expectedBookCount and set it to 3.

Spring Boot

package com.example.demo.service;

import java.util.List;

public class BookService {
    // Add expectedBookCount variable here

    public List getBooks() {
        return List.of("Spring Basics", "Java Fundamentals", "Testing Essentials");
    }
}

Need a hint?

Declare expectedBookCount as a private integer and assign it the value 3.

3

Write a test method to check book count

Create a test class called BookServiceTest in package com.example.demo.service. Inside it, write a test method called testGetBooksCount() that creates an instance of BookService and asserts that the size of the list returned by getBooks() equals expectedBookCount.

Spring Boot

// Your test class and method here

Need a hint?

Use JUnit 5 @Test annotation and assertEquals to compare expected and actual values.

4

Add Spring Boot test annotation

In the BookServiceTest class, add the @SpringBootTest annotation above the class declaration to enable Spring Boot testing support.

Spring Boot

package com.example.demo.service;

import static org.junit.jupiter.api.Assertions.assertEquals;

import org.junit.jupiter.api.Test;

// Add @SpringBootTest annotation here
public class BookServiceTest {

    @Test
    public void testGetBooksCount() {
        BookService service = new BookService();
        assertEquals(service.expectedBookCount, service.getBooks().size());
    }
}

Need a hint?

Import and add @SpringBootTest above the test class to enable Spring Boot context.