@SpringBootTest for integration tests - Mini Project: Build & Apply

Using @SpringBootTest for Integration Tests

📖 Scenario: You are building a simple Spring Boot application that manages a list of books. You want to write integration tests to check that your application context loads correctly and that your service works as expected.

🎯 Goal: Create a Spring Boot integration test class using @SpringBootTest to load the full application context and test a simple service method.

📋 What You'll Learn

Create a Spring Boot test class annotated with @SpringBootTest

Inject the BookService bean into the test class

Write a test method that calls getAllBooks() from BookService

Use assertions to verify the returned list is not null and contains expected data

💡 Why This Matters

🌍 Real World

Integration tests ensure that Spring Boot components work together correctly, catching issues early before deployment.

💼 Career

Spring Boot integration testing is a common task for backend developers to verify application behavior in a real environment.

1

Create the BookService class

Create a Spring service class called BookService with a method getAllBooks() that returns a list containing exactly these two strings: "Spring Boot Guide" and "Learning Java".

Spring Boot

# Create the BookService class with getAllBooks() method
# Your code here

Hint

Use @Service annotation and return a list with List.of().

2

Create the test class with @SpringBootTest

Create a test class called BookServiceIntegrationTest annotated with @SpringBootTest. Inside it, declare a private field bookService of type BookService and annotate it with @Autowired.

Spring Boot

import org.springframework.boot.test.context.SpringBootTest;
import org.springframework.beans.factory.annotation.Autowired;
import org.junit.jupiter.api.Test;

@SpringBootTest
public class BookServiceIntegrationTest {
    // Declare bookService here
    // Your code here
}

Hint

Use @SpringBootTest on the class and @Autowired on the service field.

3

Write a test method to call getAllBooks()

Inside BookServiceIntegrationTest, write a test method called testGetAllBooks() annotated with @Test. In this method, call bookService.getAllBooks() and store the result in a variable called books.

Spring Boot

import org.springframework.stereotype.Service;
import java.util.List;

@Service
public class BookService {
    public List getAllBooks() {
        return List.of("Spring Boot Guide", "Learning Java");
    }
}

import org.springframework.boot.test.context.SpringBootTest;
import org.springframework.beans.factory.annotation.Autowired;
import org.junit.jupiter.api.Test;

@SpringBootTest
public class BookServiceIntegrationTest {
    @Autowired
    private BookService bookService;

    @Test
    // Call getAllBooks() and store in books
    // Your code here
}

Hint

Use @Test annotation and call the service method inside the test.

4

Add assertions to verify the books list

In the testGetAllBooks() method, add assertions using org.junit.jupiter.api.Assertions to check that books is not null and that it contains exactly two items: "Spring Boot Guide" and "Learning Java".

Spring Boot

import org.springframework.stereotype.Service;
import java.util.List;

@Service
public class BookService {
    public List getAllBooks() {
        return List.of("Spring Boot Guide", "Learning Java");
    }
}

import org.springframework.boot.test.context.SpringBootTest;
import org.springframework.beans.factory.annotation.Autowired;
import org.junit.jupiter.api.Test;
import java.util.List;
import static org.junit.jupiter.api.Assertions.*;

@SpringBootTest
public class BookServiceIntegrationTest {
    @Autowired
    private BookService bookService;

    @Test
    public void testGetAllBooks() {
        List books = bookService.getAllBooks();
        // Add assertions here
        // Your code here
    }
}

Hint

Use assertNotNull, assertEquals, and assertTrue to check the list contents.

Practice

1. What is the main purpose of using @SpringBootTest in a Spring Boot project?

easy

A. To configure database connections only

B. To mock all dependencies automatically

C. To run unit tests without loading Spring context

D. To load the full application context for integration testing

Solution

1. Step 1: Understand what @SpringBootTest does

   This annotation loads the entire Spring Boot application context, allowing tests to run with all beans and configurations loaded.

2. Step 2: Compare with other testing annotations

   Unlike unit tests or mocks, @SpringBootTest is used for integration tests that need the full app context.

3. Final Answer:

   To load the full application context for integration testing -> Option D

4. Quick Check:

   @SpringBootTest = full app context load [OK]

Hint: Remember: @SpringBootTest loads full app context for integration [OK]

Common Mistakes:

• Thinking it mocks all dependencies automatically
• Confusing it with unit test annotations
• Assuming it only configures database connections

2. Which of the following is the correct way to use @SpringBootTest to start the web environment on a random port?

easy

A. @SpringBootTest(webEnv = RANDOM_PORT)

B. @SpringBootTest(webEnvironment = "random")

C. @SpringBootTest(webEnvironment = WebEnvironment.RANDOM_PORT)

D. @SpringBootTest(port = RANDOM_PORT)

Solution

1. Step 1: Recall the correct attribute name and value

   The attribute to set the web environment is webEnvironment, and the enum value for random port is WebEnvironment.RANDOM_PORT.

2. Step 2: Check syntax correctness

   @SpringBootTest(webEnvironment = WebEnvironment.RANDOM_PORT) uses the correct attribute and enum syntax. Other options use incorrect attribute names or string values.

3. Final Answer:

   @SpringBootTest(webEnvironment = WebEnvironment.RANDOM_PORT) -> Option C

4. Quick Check:

   Correct attribute and enum = @SpringBootTest(webEnvironment = WebEnvironment.RANDOM_PORT) [OK]

Hint: Use webEnvironment = WebEnvironment.RANDOM_PORT exactly [OK]

Common Mistakes:

• Using wrong attribute name like webEnv
• Passing string instead of enum
• Trying to set port directly in annotation

3. Given the following test class snippet, what will be the output when running the test?

\@SpringBootTest(webEnvironment = WebEnvironment.RANDOM_PORT)
class MyIntegrationTest {
  \@Autowired
  private TestRestTemplate restTemplate;

  \@Test
  void testHelloEndpoint() {
    String response = restTemplate.getForObject("/hello", String.class);
    System.out.println(response);
  }
}

Assuming the /hello endpoint returns "Hello, Spring!".

medium

A. Hello, Spring!

B. null

C. 404 Not Found error

D. Test fails with context load error

Solution

1. Step 1: Understand the test setup

   The test uses @SpringBootTest with RANDOM_PORT and injects TestRestTemplate, which allows calling the real HTTP endpoint.

2. Step 2: Predict the endpoint call result

   The /hello endpoint returns "Hello, Spring!" so the call will return this string and print it.

3. Final Answer:

   Hello, Spring! -> Option A

4. Quick Check:

   TestRestTemplate calls real endpoint = "Hello, Spring!" [OK]

Hint: TestRestTemplate calls real endpoint in @SpringBootTest [OK]

Common Mistakes:

• Expecting null because of missing mocks
• Assuming 404 because of wrong port
• Thinking context fails to load

4. You wrote this test but it fails with a NoSuchBeanDefinitionException for TestRestTemplate. What is the likely cause?

\@SpringBootTest
class MyTest {
  \@Autowired
  private TestRestTemplate restTemplate;

  \@Test
  void test() {
    // test code
  }
}

medium

A. TestRestTemplate is not a Spring bean

B. Missing webEnvironment setting to start web server

C. Forgot to add @Autowired annotation

D. Test class must be public

Solution

1. Step 1: Identify why TestRestTemplate bean is missing

   By default, @SpringBootTest does not start the web server unless webEnvironment is set, so TestRestTemplate bean is not created.

2. Step 2: Fix by adding webEnvironment

   Adding webEnvironment = WebEnvironment.RANDOM_PORT or DEFINED_PORT starts the server and creates the bean.

3. Final Answer:

   Missing webEnvironment setting to start web server -> Option B

4. Quick Check:

   webEnvironment needed for TestRestTemplate bean [OK]

Hint: Add webEnvironment to enable TestRestTemplate bean [OK]

Common Mistakes:

• Assuming TestRestTemplate is always available
• Forgetting to set webEnvironment in @SpringBootTest
• Thinking @Autowired is missing

5. You want to write an integration test that loads the full Spring Boot context but disables the web server startup to speed up tests. Which @SpringBootTest configuration should you use?

hard

A. @SpringBootTest(webEnvironment = WebEnvironment.NONE)

B. @SpringBootTest(webEnvironment = WebEnvironment.MOCK)

C. @SpringBootTest(webEnvironment = WebEnvironment.RANDOM_PORT)

D. @SpringBootTest(webEnvironment = WebEnvironment.DEFINED_PORT)

Solution

1. Step 1: Understand webEnvironment options

   WebEnvironment.NONE disables web server startup but loads full context. MOCK uses mock servlet environment, RANDOM_PORT and DEFINED_PORT start real servers.

2. Step 2: Choose option that disables web server

   To speed up tests without web server, use WebEnvironment.NONE.

3. Final Answer:

   @SpringBootTest(webEnvironment = WebEnvironment.NONE) -> Option A

4. Quick Check:

   Disable web server with WebEnvironment.NONE [OK]

Hint: Use WebEnvironment.NONE to skip web server startup [OK]

Common Mistakes:

• Using MOCK which still sets up servlet environment
• Starting real server with RANDOM_PORT or DEFINED_PORT
• Confusing NONE with MOCK