Spring Boot @SpringBootTest in JUnit - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to annotate the test class for Spring Boot integration testing.

JUnit

@[1]
public class MyServiceTest {
    // test methods
}

Drag options to blanks, or click blank then click option'

ASpringBootTest

BAutowired

CComponent

DService

Attempts:

3 left

💡 Hint

Common Mistakes

Using @Autowired instead of @SpringBootTest on the test class

Forgetting the @SpringBootTest annotation causes tests to run without Spring context

The @SpringBootTest annotation tells Spring Boot to look for a main configuration class and start the application context for integration testing.

2fill in blank

medium

Complete the code to inject a service bean into the test class.

JUnit

@SpringBootTest
public class MyServiceTest {
    @[1]
    private MyService myService;
}

Drag options to blanks, or click blank then click option'

AComponent

BService

CAutowired

DInject

Attempts:

3 left

💡 Hint

Common Mistakes

Using @Service instead of @Autowired for injection

Not annotating the field causes NullPointerException in tests

The @Autowired annotation tells Spring to inject the MyService bean into the test class.

3fill in blank

hard

Fix the error in the test method to assert the service returns the expected value.

JUnit

@SpringBootTest
public class MyServiceTest {
    @Autowired
    private MyService myService;

    @Test
    public void testGetValue() {
        String result = myService.getValue();
        assertEquals([1], result);
    }
}

Drag options to blanks, or click blank then click option'

AexpectedValue

B"expectedValue"

Cresult

Dnull

Attempts:

3 left

💡 Hint

Common Mistakes

Passing a variable name without quotes instead of a string literal

Swapping expected and actual arguments in assertEquals

The expected value in assertEquals must be a string literal matching the expected output, so it needs quotes.

4fill in blank

hard

Fill both blanks to create a test that checks if the application context loads successfully.

JUnit

@SpringBootTest
public class ApplicationContextTest {

    @Test
    public void contextLoads() {
        [1] context = new [2]();
        assertNotNull(context);
    }
}

Drag options to blanks, or click blank then click option'

AApplicationContext

BMyService

CApplicationContextRunner

DApplicationContextTest

Attempts:

3 left

💡 Hint

Common Mistakes

Using the test class name as a type or constructor

Using a service class instead of context classes

ApplicationContextRunner is used to create and run an application context in tests, and ApplicationContext is the interface type.

5fill in blank

hard

Fill all three blanks to write a test that verifies a bean is present in the application context.

JUnit

@SpringBootTest
public class BeanPresenceTest {

    @Autowired
    private ApplicationContext [1];

    @Test
    public void testBeanExists() {
        boolean exists = [1].containsBean([2]);
        assertTrue(exists, "Bean should be present");
    }

    private String [3]() {
        return "myService";
    }
}

Drag options to blanks, or click blank then click option'

Acontext

B"myService"

CgetBeanName

DmyService

Attempts:

3 left

💡 Hint

Common Mistakes

Passing a variable without quotes as bean name

Using inconsistent variable names for context

Not returning the correct bean name string

The ApplicationContext is injected as 'context', the bean name is passed as a string literal, and the method getBeanName returns the bean name string.

Practice

1. What is the primary purpose of using @SpringBootTest in a test class?

easy

A. To start the full Spring Boot application context for integration testing

B. To mock all dependencies automatically

C. To run only unit tests without loading Spring context

D. To disable Spring Boot features during 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 approaches

   Unlike unit tests that mock dependencies, @SpringBootTest is used for integration tests to check how components work together.

3. Final Answer:

   To start the full Spring Boot application context for integration testing -> Option A

4. Quick Check:

   @SpringBootTest = full app context [OK]

Hint: Full app context means integration test, not mocking [OK]

Common Mistakes:

• Thinking it mocks dependencies automatically
• Using it for simple unit tests
• Assuming it disables Spring Boot features

2. Which of the following is the correct way to annotate a test class to load the Spring Boot context?

easy

A. @SpringBootApplicationTest

B. @SpringBootTestOnly

C. @TestContextLoader

D. @RunWith(SpringRunner.class) @SpringBootTest

Solution

1. Step 1: Identify the standard annotations for Spring Boot tests

   The correct annotations to load Spring Boot context in JUnit 4 are @RunWith(SpringRunner.class) and @SpringBootTest.

2. Step 2: Check the other options

   Options B, C, and D are not valid Spring Boot or JUnit annotations.

3. Final Answer:

   @RunWith(SpringRunner.class) @SpringBootTest -> Option D

4. Quick Check:

   Use @RunWith(SpringRunner.class) with @SpringBootTest [OK]

Hint: Remember: @RunWith + @SpringBootTest for context loading [OK]

Common Mistakes:

• Using non-existent annotations
• Forgetting @RunWith in JUnit 4
• Confusing with @SpringBootApplication

3. Given the following test class, what will be the output when the test runs successfully?

\@SpringBootTest
class MyServiceTest {
    \@Autowired
    private MyService myService;

    \@Test
    void testService() {
        assertNotNull(myService);
        System.out.println("Service is loaded");
    }
}

medium

A. Test passes and prints 'Service is loaded'

B. Test fails because myService is null

C. Compilation error due to missing annotations

D. Test passes but prints nothing

Solution

1. Step 1: Understand what @SpringBootTest does here

   The annotation loads the full Spring context, so myService bean is injected and not null.

2. Step 2: Analyze the test method

   The assertion assertNotNull(myService) passes, and the print statement outputs "Service is loaded".

3. Final Answer:

   Test passes and prints 'Service is loaded' -> Option A

4. Quick Check:

   Bean injected + assertNotNull = pass and print [OK]

Hint: If context loads, @Autowired bean is not null [OK]

Common Mistakes:

• Assuming myService is null without context
• Forgetting that @SpringBootTest loads beans
• Confusing compilation errors with runtime behavior

4. You have a test annotated with @SpringBootTest but it fails with a NoSuchBeanDefinitionException. What is the most likely cause?

medium

A. The test method is private

B. The test class is missing @Test annotation

C. The bean is not defined or scanned in the application context

D. The Spring Boot version is outdated

Solution

1. Step 1: Understand the exception meaning

   NoSuchBeanDefinitionException means Spring could not find a bean of the required type in the context.

2. Step 2: Identify common reasons for missing beans

   This usually happens if the bean is not defined, not annotated with @Component/@Service, or not in a scanned package.

3. Final Answer:

   The bean is not defined or scanned in the application context -> Option C

4. Quick Check:

   Missing bean definition = NoSuchBeanDefinitionException [OK]

Hint: Missing bean means not defined or scanned [OK]

Common Mistakes:

• Blaming test method visibility
• Assuming missing @Test causes bean errors
• Thinking Spring Boot version causes missing bean

5. You want to speed up your test suite by loading only a part of the Spring Boot context. Which approach can you use with @SpringBootTest to limit the loaded beans?

hard

A. Remove @SpringBootTest and use plain JUnit tests

B. Use @SpringBootTest(classes = YourConfig.class) to load only specific configuration

C. Add @MockBean to all beans manually

D. Use @SpringBootTest with @Transactional only

Solution

1. Step 1: Understand how to limit context loading

   By specifying classes attribute in @SpringBootTest, you can load only selected configuration classes, reducing context size.

2. Step 2: Evaluate other options

   Removing @SpringBootTest disables context loading, @MockBean mocks beans but does not limit context size, and @Transactional controls transactions, not context loading.

3. Final Answer:

   Use @SpringBootTest(classes = YourConfig.class) to load only specific configuration -> Option B

4. Quick Check:

   Limit context by specifying classes in @SpringBootTest [OK]

Hint: Specify classes attribute to limit context [OK]

Common Mistakes:

• Thinking @MockBean reduces context size
• Removing @SpringBootTest disables context, not limits
• Confusing @Transactional with context loading