TestRestTemplate for full integration in Spring Boot - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to autowire TestRestTemplate in a Spring Boot test class.

Spring Boot

@Autowired
private [1] restTemplate;

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

ATestRestTemplate

BWebClient

CRestTemplate

DHttpClient

Attempts:

3 left

💡 Hint

Common Mistakes

Using RestTemplate instead of TestRestTemplate

Using WebClient which is reactive

Using HttpClient which is not Spring-specific

TestRestTemplate is the correct class to autowire for integration testing in Spring Boot.

2fill in blank

medium

Complete the code to send a GET request to '/api/items' using TestRestTemplate.

Spring Boot

ResponseEntity<String> response = restTemplate.[1]("/api/items");

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

AgetForEntity

BpostForEntity

Cexchange

Dput

Attempts:

3 left

💡 Hint

Common Mistakes

Using postForEntity for GET requests

Using put which is for updates

Using exchange without specifying HTTP method

getForEntity sends a GET request and returns a ResponseEntity.

3fill in blank

hard

Fix the error in the assertion to check if the response status is 200 OK.

Spring Boot

assertEquals(HttpStatus.[1], response.getStatusCode());

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

ANOT_FOUND

BCREATED

COK

DBAD_REQUEST

Attempts:

3 left

💡 Hint

Common Mistakes

Using NOT_FOUND (404) instead of OK

Using BAD_REQUEST (400)

Using CREATED (201) which is for POST

HttpStatus.OK represents the 200 status code for successful GET requests.

4fill in blank

hard

Fill both blanks to send a POST request with a JSON body and receive a response as a String.

Spring Boot

ResponseEntity<String> response = restTemplate.[1]("/api/items", [2], String.class);

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

ApostForEntity

BnewItem

CgetForEntity

DHttpEntity

Attempts:

3 left

💡 Hint

Common Mistakes

Using getForEntity for POST

Trying to use HttpEntity with postForEntity (pass body directly)

Confusing newItem as a method

postForEntity sends a POST request. Pass the request body (newItem) directly as an object or JSON string.

5fill in blank

hard

Fill all three blanks to create a TestRestTemplate with basic authentication and send a GET request.

Spring Boot

TestRestTemplate restTemplate = new TestRestTemplate().withBasicAuth("[1]", "[2]");
ResponseEntity<String> response = restTemplate.[3]("/api/secure");

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

Auser

Bpassword

CgetForEntity

DpostForEntity

Attempts:

3 left

💡 Hint

Common Mistakes

Using postForEntity for GET requests

Swapping username and password

Leaving authentication blank

Use new TestRestTemplate().withBasicAuth(username, password) for basic auth. getForEntity sends a GET request.

Practice

1. What is the main purpose of TestRestTemplate in a Spring Boot application?

easy

A. To perform real HTTP requests for full integration testing

B. To mock database calls during unit tests

C. To replace the main application context

D. To generate API documentation automatically

Solution

1. Step 1: Understand TestRestTemplate's role

   TestRestTemplate is designed to send HTTP requests to the running Spring Boot app during tests.

2. Step 2: Compare with other testing tools

   Unlike mocks or stubs, it tests the full app stack by making real HTTP calls.

3. Final Answer:

   To perform real HTTP requests for full integration testing -> Option A

4. Quick Check:

   TestRestTemplate = real HTTP requests [OK]

Hint: Remember: TestRestTemplate tests full app via HTTP [OK]

Common Mistakes:

• Confusing TestRestTemplate with mocking tools
• Thinking it replaces application context
• Assuming it auto-generates docs

2. Which annotation combination is correct to enable TestRestTemplate with a random port in a Spring Boot test?

easy

A. @SpringBootTest(webEnvironment = WebEnvironment.MOCK)

B. @SpringBootTest(webEnvironment = WebEnvironment.NONE)

C. @SpringBootTest(webEnvironment = WebEnvironment.RANDOM_PORT)

D. @SpringBootTest(webEnvironment = WebEnvironment.DEFINED_PORT)

Solution

1. Step 1: Identify webEnvironment for real HTTP tests

   Using RANDOM_PORT starts the server on a random port for real HTTP calls.

2. Step 2: Understand other options

   NONE disables web environment, MOCK uses mock servlet environment, DEFINED_PORT uses fixed port.

3. Final Answer:

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

4. Quick Check:

   RANDOM_PORT enables real HTTP server [OK]

Hint: Use RANDOM_PORT for real HTTP server in tests [OK]

Common Mistakes:

• Using MOCK disables real HTTP server
• Choosing NONE disables web environment
• Assuming DEFINED_PORT is random

3. Given this test snippet using TestRestTemplate:

var response = restTemplate.getForEntity("/api/greet", String.class);
System.out.println(response.getStatusCodeValue());
System.out.println(response.getBody());

If the endpoint /api/greet returns HTTP 200 and body "Hello!", what will be printed?

medium

A. 200\nnull

B. 404\nNot Found

C. 500\nInternal Server Error

D. 200\nHello!

Solution

1. Step 1: Understand getForEntity behavior

   It sends GET request and returns response with status and body.

2. Step 2: Match expected endpoint response

   The endpoint returns 200 status and "Hello!" body, so these print exactly.

3. Final Answer:

   200\nHello! -> Option D

4. Quick Check:

   Status 200 and body "Hello!" printed [OK]

Hint: Response status and body print as returned by endpoint [OK]

Common Mistakes:

• Assuming 404 if endpoint not found in test
• Expecting null body when response is valid
• Confusing status code with body content

4. Consider this test code snippet:

@Autowired
private TestRestTemplate restTemplate;

@Test
public void testGetUser() {
  var response = restTemplate.getForEntity("/users/1", User.class);
  assertEquals(200, response.getStatusCodeValue());
}

If the test fails with a NullPointerException on restTemplate.getForEntity, what is the most likely cause?

medium

A. The test method is missing @Test annotation

B. TestRestTemplate was not injected because @SpringBootTest annotation is missing

C. User class is not serializable

D. The endpoint /users/1 does not exist

Solution

1. Step 1: Identify cause of NullPointerException

   NullPointerException on restTemplate means it was never set (null).

2. Step 2: Check test setup annotations

   Without @SpringBootTest, Spring does not create context or inject beans like TestRestTemplate.

3. Final Answer:

   TestRestTemplate was not injected because @SpringBootTest annotation is missing -> Option B

4. Quick Check:

   Missing @SpringBootTest causes null injection [OK]

Hint: NullPointer on restTemplate means missing @SpringBootTest [OK]

Common Mistakes:

• Blaming missing endpoint for NullPointerException
• Assuming serialization error causes NPE
• Forgetting to add @Test annotation

5. You want to write a full integration test using TestRestTemplate that posts JSON data to /api/items and verifies the created item's ID is returned. Which code snippet correctly performs this test?

hard

A. var item = new Item(null, "Book");
var response = restTemplate.postForEntity("/api/items", item, Item.class);
assertEquals(201, response.getStatusCodeValue());
assertNotNull(response.getBody().getId());

B. var item = new Item(null, "Book");
var response = restTemplate.getForEntity("/api/items", Item.class);
assertEquals(201, response.getStatusCodeValue());

C. var item = new Item(null, "Book");
var response = restTemplate.postForObject("/api/items", item, Item.class);
assertEquals(404, response.getStatusCodeValue());

D. var item = new Item(null, "Book");
var response = restTemplate.exchange("/api/items", HttpMethod.GET, null, Item.class);
assertEquals(201, response.getStatusCodeValue());

Solution

1. Step 1: Identify correct HTTP method for creating resource

   POST is used to create new items, so postForEntity is appropriate.

2. Step 2: Verify response status and body

   201 status means created; response body should contain new item's ID, so assertNotNull on getId() is correct.

3. Final Answer:

   Code snippet using postForEntity with POST and checking 201 and ID -> Option A

4. Quick Check:

   POST + 201 + returned ID = correct test [OK]

Hint: Use postForEntity and check 201 plus returned ID [OK]

Common Mistakes:

• Using GET instead of POST for creation
• Expecting 404 instead of 201 status
• Using postForObject without status check