Test profiles and configuration in Spring Boot - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ component_behavior

intermediate

What is the active profile output?

Given a Spring Boot application with two profiles dev and prod, and the following configuration:

application.properties:
spring.profiles.active=dev

application-dev.properties:
app.message=Development Mode

application-prod.properties:
app.message=Production Mode

@Component
public class MessagePrinter {
  @Value("${app.message}")
  private String message;

  public String getMessage() {
    return message;
  }
}

What will getMessage() return when the application runs?

A Development Mode

B Production Mode

C app.message

D null

💡 Hint

Check which profile is active in application.properties.

The active profile is set to 'dev', so Spring loads application-dev.properties. The app.message value is 'Development Mode'.

📝 Syntax

intermediate

Which configuration activates the 'test' profile correctly?

You want to activate the 'test' profile in a Spring Boot application. Which of the following ways correctly activates the profile?

A Set environment variable SPRING_PROFILES_ACTIVE=test

B Add <code>spring.profiles.active=test</code> in <code>application-test.properties</code>

C Add <code>@Profile("test")</code> on the main application class

D Set <code>spring.profiles.include=test</code> in <code>application.properties</code>

💡 Hint

Activating a profile means telling Spring which profile to use when starting.

Setting the environment variable SPRING_PROFILES_ACTIVE=test activates the 'test' profile globally. Adding the property inside application-test.properties does not activate it by itself.

🔧 Debug

advanced

Why does the bean not load for 'prod' profile?

Consider this Spring Boot bean:

@Component
@Profile("prod")
public class ProdService {
  // service code
}

When running with the 'dev' profile active, the application fails to find ProdService and throws a NoSuchBeanDefinitionException. Why?

A Because @Profile only works on configuration classes, not components

B Because the bean class is missing the @Service annotation

C Because the 'prod' profile is not active, so the bean is not created

D Because the bean requires a constructor argument that is missing

💡 Hint

Check which profile is active and how @Profile works.

The @Profile("prod") annotation means the bean is only created when the 'prod' profile is active. With 'dev' active, Spring skips this bean.

❓ state_output

advanced

What is the value of 'timeout' after loading profiles?

Given these property files:

application.properties:
timeout=30

application-dev.properties:
timeout=10

application-prod.properties:
timeout=60

And the active profile is set to 'prod'. What is the value of timeout injected by @Value("${timeout}")?

A 10

B 30

C null

D 60

💡 Hint

Profile-specific properties override default properties.

The 'prod' profile is active, so application-prod.properties overrides timeout to 60.

🧠 Conceptual

expert

How does Spring Boot resolve multiple active profiles with conflicting properties?

If you set multiple active profiles like spring.profiles.active=dev,prod and both profiles define the same property app.mode with different values, which value does Spring Boot use?

A The value from the first profile listed in <code>spring.profiles.active</code> is used

B The value from the last profile listed in <code>spring.profiles.active</code> is used

C Spring Boot throws an error due to conflicting properties

D Spring Boot merges both values into a list

💡 Hint

Think about the order Spring Boot loads profile properties.

Spring Boot loads profiles in order and later profiles override earlier ones. So the last profile's property wins.

Practice

1. What is the main purpose of using test profiles in a Spring Boot application?

easy

A. To run the application with special settings only during testing

B. To improve the application's runtime performance in production

C. To automatically generate test data for the application

D. To disable security features permanently

Solution

1. Step 1: Understand test profiles concept

   Test profiles allow running the app with different settings specifically for testing purposes.

2. Step 2: Compare options

   Only To run the application with special settings only during testing correctly describes the purpose of test profiles as special settings for tests.

3. Final Answer:

   To run the application with special settings only during testing -> Option A

4. Quick Check:

   Test profiles = special test settings [OK]

Hint: Test profiles isolate test settings from production [OK]

Common Mistakes:

• Confusing test profiles with performance tuning
• Thinking test profiles generate test data automatically
• Assuming test profiles disable security permanently

2. Which of the following is the correct way to name a properties file for a test profile named testdb?

easy

A. application.properties.testdb

B. testdb-application.properties

C. application-testdb.properties

D. application_testdb.properties

Solution

1. Step 1: Recall Spring Boot profile file naming

   Spring Boot uses the pattern application-{profile}.properties for profile-specific config files.

2. Step 2: Match the pattern with the profile name

   For profile testdb, the correct file name is application-testdb.properties.

3. Final Answer:

   application-testdb.properties -> Option C

4. Quick Check:

   Profile file = application-{profile}.properties [OK]

Hint: Use application-{profile}.properties naming [OK]

Common Mistakes:

• Placing profile name after .properties
• Using underscores instead of hyphens
• Reversing the order of profile and application

3. Given the following test class annotation:
@ActiveProfiles("test")
and two property files:
application.properties with db.url=prod-db
application-test.properties with db.url=test-db
What will be the value of db.url during this test?

medium

A. prod-db

B. test-db

C. null

D. application.properties

Solution

1. Step 1: Understand @ActiveProfiles effect

   @ActiveProfiles("test") activates the 'test' profile for the test run.

2. Step 2: Determine property file precedence

   Properties in application-test.properties override those in application.properties when 'test' profile is active.

3. Final Answer:

   test-db -> Option B

4. Quick Check:

   Active profile properties override default [OK]

Hint: Active profile properties override defaults [OK]

Common Mistakes:

• Assuming default properties always apply
• Confusing profile name in annotation
• Expecting null if profile is active

4. You have a test annotated with @ActiveProfiles("dev") but the test still uses properties from application.properties instead of application-dev.properties. What is the most likely cause?

medium

A. The test class must extend a special base class to use profiles

B. The @ActiveProfiles annotation is only for production

C. Spring Boot does not support multiple profiles

D. The application-dev.properties file is missing or misnamed

Solution

1. Step 1: Check profile file presence

   If application-dev.properties is missing or named incorrectly, Spring Boot falls back to application.properties.

2. Step 2: Verify annotation usage

   @ActiveProfiles works for tests to activate profiles; it is not limited to production.

3. Final Answer:

   The application-dev.properties file is missing or misnamed -> Option D

4. Quick Check:

   Missing profile file causes fallback to default [OK]

Hint: Check profile file name and location first [OK]

Common Mistakes:

• Thinking @ActiveProfiles is ignored in tests
• Believing Spring Boot lacks profile support
• Assuming inheritance is required for profiles

5. You want to run integration tests with a profile integration that uses a different database URL and disables security. Which combination correctly activates this profile and overrides the default settings?

hard

A. Create application-integration.properties with overrides and annotate tests with @ActiveProfiles("integration")

B. Add spring.profiles.active=integration only in application.properties

C. Use @Profile("integration") on the test class without any properties file

D. Set environment variable SPRING_PROFILE=integration but keep default properties unchanged

Solution

1. Step 1: Use profile-specific properties file

   Create application-integration.properties to override database URL and security settings for the integration profile.

2. Step 2: Activate profile in tests

   Annotate tests with @ActiveProfiles("integration") to activate the profile during test runs.

3. Final Answer:

   Create application-integration.properties with overrides and annotate tests with @ActiveProfiles("integration") -> Option A

4. Quick Check:

   Profile file + @ActiveProfiles activates test config [OK]

Hint: Use profile file plus @ActiveProfiles to activate [OK]

Common Mistakes:

• Setting active profile only in default properties
• Using @Profile instead of @ActiveProfiles on tests
• Relying on environment variable without config changes