TestRestTemplate for full integration in Spring Boot - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ component_behavior

intermediate

What is the output of this TestRestTemplate GET request?

Given a Spring Boot REST controller that returns a JSON object {"message": "Hello World"} at endpoint /greet, what will this TestRestTemplate call return?

Spring Boot

ResponseEntity<String> response = testRestTemplate.getForEntity("/greet", String.class);
String body = response.getBody();
System.out.println(body);

A {"msg":"Hello World"}

B {"message":"Hello World"}

C null

D Hello World

💡 Hint

Remember the controller returns a JSON object with key 'message'.

The controller returns a JSON object with key 'message' and value 'Hello World'. The TestRestTemplate getForEntity returns the raw JSON string in the body.

❓ state_output

intermediate

What is the HTTP status code after a successful POST with TestRestTemplate?

A Spring Boot controller accepts POST requests at /items and returns ResponseEntity with status CREATED (201). What status code will testRestTemplate.postForEntity("/items", newItem, Item.class).getStatusCodeValue() return?

Spring Boot

ResponseEntity<Item> response = testRestTemplate.postForEntity("/items", newItem, Item.class);
int statusCode = response.getStatusCodeValue();
System.out.println(statusCode);

A 201

B 404

C 200

D 500

💡 Hint

Check the controller's ResponseEntity status for POST.

The controller returns ResponseEntity with status CREATED (201), so the TestRestTemplate response status code is 201.

📝 Syntax

advanced

Which TestRestTemplate call correctly sends a PUT request with a JSON body?

You want to update an item at /items/5 using TestRestTemplate. Which option correctly sends a PUT request with the updated item object?

A testRestTemplate.exchange("/items/5", HttpMethod.PUT, new HttpEntity<>(updatedItem), Item.class);

B testRestTemplate.put("/items/5", updatedItem, Item.class);

C testRestTemplate.put("/items/5", updatedItem);

D testRestTemplate.postForEntity("/items/5", updatedItem, Item.class);

💡 Hint

PUT requests with body often use exchange method with HttpEntity.

Option A uses exchange with HttpMethod.PUT and HttpEntity wrapping the updatedItem, which is the correct way to send a PUT with body. Option A is valid but does not return a response. Option A is invalid because put method does not take a response type. Option A uses POST instead of PUT.

🔧 Debug

advanced

Why does this TestRestTemplate call throw a 404 error?

Given this code: ResponseEntity response = testRestTemplate.getForEntity("/api/data", String.class); The server returns 404 Not Found. What is the most likely cause?

A The server is down during the test.

B The testRestTemplate is not autowired correctly.

C The response type String.class is invalid for getForEntity.

D The endpoint /api/data is not mapped in the controller.

💡 Hint

404 means resource not found on server.

A 404 error means the requested URL is not mapped to any controller method. Other options cause different errors or exceptions.

🧠 Conceptual

expert

What is the main advantage of using TestRestTemplate in full integration tests?

Why do developers prefer TestRestTemplate for full integration testing of Spring Boot REST APIs instead of mocking controllers?

A It allows testing controller methods without starting the server.

B It automatically mocks all dependencies for faster tests.

C It tests the entire HTTP stack including serialization, filters, and controller logic in a running server.

D It only tests the service layer without HTTP involvement.

💡 Hint

Think about what full integration means versus unit testing.

TestRestTemplate sends real HTTP requests to a running Spring Boot server, testing serialization, filters, security, and controller logic together. Mocking skips many layers.