40 Rest Assured API Testing Interview Questions (2023)

In this article, we’ve compiled a list of Rest Assured API testing interview questions and provided detailed answers for fresher for experienced to help you prepare effectively. API testing is a crucial part of modern software development and quality assurance processes. When it comes to testing RESTful APIs in Java-based projects, Rest Assured is a popular and powerful tool of choice. If you’re preparing for an interview for an API testing role or a position that involves using Rest Assured, you’ll likely encounter questions that assess your knowledge and skills in Rest Assured API testing.

Rest Assured API Interview Questions and Answers

1. What is Rest Assured, and why is it used for API testing?

Answer: Rest Assured is a Java-based library for automating and testing RESTful APIs. It simplifies the process of sending HTTP requests, validating responses, and performing assertions on API endpoints. Rest Assured is widely use for API testing because it provides a fluent and expressive API that makes writing tests easy and readable.

2. How do you set up Rest Assured in a Java project, and what are the necessary dependencies?

Answer: To set up Rest Assured in a Java project:

Add the Rest Assured dependency to your project’s build file (e.g., Gradle or Maven).
Import necessary classes from the Rest Assured library in your Java code.

For Gradle, the dependency might look like this:

dependencies {
implementation 'io.rest-assured:rest-assured:4.4.0'
}

For Maven, add this to your ‘pom.xml‘:

<dependency> <groupId>io.rest-assured</groupId>                                                                          <artifactId>rest-assured</artifactId>                                                                                 <version>4.4.0</version>                                                                                                                                                                                                        </dependency>

3. How do you send a GET request using Rest Assured, and how do you validate the response?

Answer: To send a GET request using Rest Assured:

import io.restassured.RestAssured;
import io.restassured.response.Response;                                                                           Response response = RestAssured.get("https://api.example.com/resource");                            // To validate the response status code (e.g., 200 OK):
response.then().statusCode(200);                                                                                                 // To validate response body (e.g., JSON):
response.then().body("key", equalTo("expectedValue"));

You can use various methods provided by Rest Assured’s ‘Response‘ object to validate different aspects of the response, such as headers, cookies, and more.

4. Explain the purpose of Rest Assured’s given-when-then structure in API testing.

Answer: Rest Assured promotes a clear and expressive way of writing API tests using the given-when-then structure:

Given: This is where you set up the initial conditions for the test, such as headers, request parameters, or authentication.
When: This is where you perform the actual HTTP request (e.g., GET, POST, PUT).
Then: In this section, you define assertions and validations on the response to ensure it meets the expected criteria.

This structure improves the readability of tests and separates concerns, making it easier to understand the purpose of each test step.

5. How can you pass query parameters in a Rest Assured GET request?

Answer: You can pass query parameters in a Rest Assured GET request using the ‘param‘ method:

Response response = RestAssured
.given()
.param("paramName", "paramValue")
.when()
.get("https://api.example.com/resource");

You can chain multiple 'param' methods to add multiple query parameters.

6. Explain how to send a POST request with a JSON payload using Rest Assured.

Answer: To send a POST request with a JSON payload using Rest Assured:

import io.restassured.RestAssured;
import io.restassured.http.ContentType;                                                                                      String requestBody = "{\"key\": \"value\"}";                                                                        Response response = RestAssured
.given()
.contentType(ContentType.JSON) // Set content type to JSON
.body(requestBody) // Set the request body
.when()
.post("https://api.example.com/resource");                                                                                        // Validate the response as needed

Ensure that you set the ‘Content-Type‘ header to JSON and provide the JSON payload in the request body.

7. How do you handle authentication in Rest Assured?

Answer: Rest Assured provides methods to handle various types of authentication, including Basic Authentication and OAuth. For Basic Authentication:

import io.restassured.RestAssured;
import io.restassured.authentication.BasicAuthScheme;                                                                                                      BasicAuthScheme authScheme = new BasicAuthScheme();
authScheme.setUserName("username");
authScheme.setPassword("password");                                                                                                                              Response response = RestAssured
.given()
.auth().basic("username", "password")
.when()
.get("https://api.example.com/resource");                                                                                          // Validate the response

For OAuth, you would set up the appropriate OAuth scheme and provide the necessary tokens.

8. What is request specification in Rest Assured, and how does it simplify API testing?

Answer: A request specification in Rest Assured is a reusable configuration that allows you to define common settings and headers for API requests. It simplifies API testing by eliminating the need to repeatedly specify the same settings for multiple requests. You can create a request specification once and reuse it across multiple tests.

9. How do you extract data from a JSON response in Rest Assured?

Answer: You can extract data from a JSON response in Rest Assured using the ‘jsonPath‘ method:

import io.restassured.RestAssured;                                                                                                         String responseBody = RestAssured
.get("https://api.example.com/resource")
.then()
.extract()
.response()
.asString();                                                                                                                                                String extractedValue = RestAssured
.given()
.param("paramName", "paramValue")
.when()
.get("https://api.example.com/resource")
.then()
.extract()
.path("key");

You can use 'jsonPath' to navigate the JSON structure and extract specific values.

10. What is Rest Assured’s response specification, and why is it valuable in API testing?

Answer: A response specification in Rest Assured is a reusable configuration that defines common expectations and validations for API responses. It is valuable in API testing because it allows you to define expected status codes, response content types, and other response-related criteria once and reuse them across multiple tests. This promotes consistency and reduces redundancy in test code.

11. How can you handle dynamic values in API responses, such as timestamps or unique identifiers, when writing Rest Assured tests?

Answer: To handle dynamic values in API responses, you can use Rest Assured’s flexible matching mechanisms, such as:

Ignoring specific fields during response validation.
Using wildcard matches for dynamic or unpredictable data.
Extracting dynamic values and storing them in variables for later use in assertions.

12. Explain how you can perform API testing for endpoints that require multipart file uploads in Rest Assured.

Answer: To perform API testing for endpoints that require multipart file uploads in Rest Assured:

import io.restassured.RestAssured;
import io.restassured.http.ContentType;
import org.testng.annotations.Test;                                                                                                                                                                                          import java.io.File;                                                                                                                                                                                                                                                                                                                                                                                           public class FileUploadTest {                                                                                                                                                             @Test
public void testFileUpload() {
    File fileToUpload = new File("path/to/your/file.txt");

    RestAssured
        .given()
        .multiPart("file", fileToUpload, "text/plain")
        .when()
        .post("https://api.example.com/upload-endpoint")
        .then()
        .statusCode(200);
}                                                                                                                                                                                                                            }

You can use the ‘multiPart‘ method to attach files to the request.

13. How do you handle API testing scenarios that involve handling cookies in Rest Assured?

Answer: Rest Assured provides methods to handle cookies in API testing. To handle cookies:

Use the ‘cookie‘ method to set and retrieve cookies in the request and response.
Perform cookie-related validations using assertions to ensure cookies are correctly set and received.

14. What is Rest Assured’s logging feature, and how can it assist in debugging API tests?

Answer: Rest Assured’s logging feature allows you to log request and response details, including headers, bodies, and other relevant information. It assists in debugging API tests by providing a clear view of the communication between your tests and the API server. You can enable logging at various levels, such as ‘ALL', ‘HEADERS‘, or ‘BODY‘, to capture the desired level of detail.

15. Explain how you can perform API testing for pagination, where you need to retrieve multiple pages of data using Rest Assured.

Answer: To perform API testing for pagination in Rest Assured:

Send the initial request to fetch the first page of data.
Extract information about pagination, such as next page URLs or tokens, from the response.
Use a loop to automate subsequent requests, following the pagination information until all data is retrieved and tested.

You can use variables to keep track of the next page URLs or tokens and update them in each iteration.

16. How can you handle timeouts in Rest Assured requests, and why is it important?

Answer: You can handle timeouts in Rest Assured requests using the ‘timeout‘ method to specify the maximum time allowed for a request to complete. Timeout handling is important in API testing to ensure that tests do not hang indefinitely and that response times are within acceptable limits.

RestAssured
.given()
.urlEncodingEnabled(false) // Disable URL encoding for the path parameter
.pathParam("paramName", "paramValue")
.when()
.get("https://api.example.com/resource/{paramName}")
.then()
.statusCode(200);

17. What is Rest Assured’s support for BDD (Behavior-Driven Development), and how does it improve test readability?

Answer: Rest Assured provides support for BDD-style testing using natural language constructs like ‘given()‘, ‘when()‘, and ‘then()‘. This improves test readability by making test code more closely resemble plain English sentences, making it easier for non-technical stakeholders to understand the test scenarios.

given()
.param("paramName", "paramValue")
when()
.get("https://api.example.com/resource")
then()
.statusCode(200);

18. How do you handle dynamic authentication tokens that change frequently in API testing with Rest Assured?

Answer: To handle dynamic authentication tokens in Rest Assured:

Extract the token from the response using ‘jsonPath‘ or other methods.
Store the token in a variable.
Use the stored token in subsequent requests for authentication.

String token = RestAssured
.given()
.param("username", "user")
.param("password", "pass")
.when()
.post("https://api.example.com/authenticate")
.then()
.statusCode(200)
.extract()
.path("token");                                                                                                                                                                                                                                                 RestAssured
.given()
.header("Authorization", "Bearer " + token)
.when()
.get("https://api.example.com/protected-resource")
.then()
.statusCode(200);

19. Explain the purpose of Rest Assured filters, and how can they be used in API testing?

Answer: Rest Assured filters use to intercept and manipulate requests and responses in API testing. They are valuable for scenarios where you need to customize or log the request/response details or perform pre-processing/post-processing tasks. Filters can be added to Rest Assured to perform actions before and after requests are sent and received.

20. How can you parameterize Rest Assured tests to run with different sets of data?

Answer: You can parameterize Rest Assured tests using TestNG or JUnit data-driven testing features. For example, in TestNG, you can use the ‘@DataProvider' annotation to provide different sets of data to a test method, enabling multiple test executions with varying input data.

@DataProvider(name = "testData")
public Object[][] testData() {
return new Object[][] {
{"param1", "value1"},
{"param2", "value2"},
// Add more data sets as needed
};
}                                                                                                                                                                     @Test(dataProvider = "testData")
public void testApi(String param, String value) {
RestAssured
.given()
.param(param, value)
.when()
.get("https://api.example.com/resource")
.then()
.statusCode(200);
}

21. How do you handle API testing scenarios that involve handling different HTTP methods (e.g., GET, POST, PUT, DELETE) in Rest Assured?

Answer: To handle different HTTP methods in Rest Assured:

Use the corresponding method (‘get()‘, ‘post()‘, ‘put()‘, ‘delete()‘, etc.) to specify the desired HTTP method for the request.
Define request parameters, headers, and the request body as needed for each specific method.
Perform assertions and validations based on the expected behavior for that method.

22. What is the purpose of Rest Assured’s ‘expect() method, and how can it be used in API testing?

Answer: Rest Assured’s ‘expect()‘ method is used to specify expectations for API responses in a more fluent and readable way. It allows you to define assertions and validations directly within the test flow, improving test clarity and conciseness.

expect()
.statusCode(200)
.body("key", equalTo("expectedValue"))
.header("Content-Type", "application/json")
.when()
.get("https://api.example.com/resource");

23. How can you simulate error scenarios and test error handling in Rest Assured API tests?

Answer: To simulate error scenarios and test error handling in Rest Assured:

Send requests that expect to produce error responses (e.g., invalid input, unauthorized access).
Use assertions to validate the correct status codes, error messages, and response structures as defined in the API’s documentation.

RestAssured
.given()
.param("invalidParam", "invalidValue")
.when()
.get("https://api.example.com/error-endpoint")
.then()
.statusCode(400)
.body("error.message", equalTo("Invalid parameter"));

24. How can you handle testing scenarios that involve handling different content types (e.g., JSON, XML) in Rest Assured?

Answer: To handle different content types in Rest Assured:

Set the ‘Content-Type‘ header to specify the desired content type for request payloads (if applicable).
Use Rest Assured’s ‘contentType()‘ method to specify the expected content type in response validations.
Customize request and response handling based on the content type, such as parsing XML or JSON responses accordingly.

RestAssured
.given()
.contentType(ContentType.JSON)
.body("{ \"key\": \"value\" }")
.when()
.post("https://api.example.com/resource")
.then()
.contentType(ContentType.JSON)
.statusCode(201);

25. Explain how you would handle API testing for endpoints that require authentication tokens to be included in the request header in Rest Assured.

Answer: To handle API testing for endpoints that require authentication tokens in the request header:

Extract the authentication token (e.g., JWT, OAuth token) from a previous request or another source.
Set the ‘Authorization‘ header with the token value in the request using the ‘header()‘ method.

String token = "your-auth-token";                                                                                                                    RestAssured
.given()
.header("Authorization", "Bearer " + token)
.when()
.get("https://api.example.com/protected-resource")
.then()
.statusCode(200);

26. What is the purpose of Rest Assured’s ‘given().filter()‘ method, and how can it be used in API testing?

Answer: Rest Assured’s ‘given()'.'filter()‘ method is used to apply custom filters to the request or response. Filters allow you to perform tasks such as logging, modifying headers, or handling specific scenarios (e.g., authentication) before or after the request is sent. This is particularly useful for customizing request and response behavior in a flexible manner.

RestAssured
.given()
.filter(requestFilter) // Apply a custom request filter
.when()
.get("https://api.example.com/resource")
.then()
.statusCode(200);

27. How can you handle API testing scenarios that involve testing file downloads in Rest Assured?

Answer: To handle API testing scenarios that involve testing file downloads in Rest Assured:

Send a request to the API endpoint that triggers the file download.
Validate the response status code (e.g., 200 OK).
Use the response to access and verify the downloaded file content or its properties.

Response response = RestAssured
.when()
.get("https://api.example.com/download-endpoint");                                                                              response.then()
.statusCode(200);                                                                                                                                                                                                // Validate the downloaded file content, size, or metadata as needed

28. What is Rest Assured’s support for handling redirects in API testing, and how can it be used?

Answer: Rest Assured supports handling redirects by default. When you send a request, Rest Assured will automatically follow redirects and return the final response. You can use the ‘statusCode()‘ method to ensure that the final response has the expected status code, which includes following any redirects that occurred.

RestAssured
.when()
.get("https://api.example.com/redirect-endpoint")
.then()
.statusCode(200); // Ensure that the final response is 200 OK

29. How can you perform API testing for endpoints that require sending cookies in Rest Assured requests?

Answer: To perform API testing for endpoints that require sending cookies in Rest Assured requests:

Use the ‘cookie‘ method to set cookies in the request.
Validate the presence and values of cookies in the response using assertions.

RestAssured
.given()
.cookie("sessionId", "your-cookie-value")
.when()
.get("https://api.example.com/cookie-endpoint")
.then()
.statusCode(200)
.cookie("responseCookieName", "expectedCookieValue");

30. Explain the purpose of Rest Assured’s ‘log()‘ method, and how can it assist in debugging API tests?

Answer: Rest Assured’s ‘log()‘ method is used to log request and response details, including headers, bodies, and other relevant information. It assists in debugging API tests by providing a detailed log of the interactions between your tests and the API server. You can use different logging levels (‘ALL‘, ‘HEADERS‘, ‘BODY‘, etc.) to control the level of detail in the logs.

RestAssured
.given()
.log().all() // Log all request and response details
.when()
.get("https://api.example.com/resource")
.then()
.statusCode(200);

31. How can you handle testing scenarios where API responses include binary data, such as images or PDF files?

Answer: To handle testing scenarios where API responses include binary data, such as images or PDF files:

Retrieve the binary data as a byte array or input stream from the response.
Validate the content, size, or other properties of the binary data as needed.

byte[] binaryData = RestAssured
.when()
.get("https://api.example.com/binary-endpoint")
.then()
.statusCode(200)
.extract()
.asByteArray();                                                                                                                                                                            // Validate binary data properties or save it to a file for further inspection

32. How do you handle API testing for endpoints that require sending custom request headers in Rest Assured?

Answer: To handle API testing for endpoints that require sending custom request headers in Rest Assured:

Use the ‘header()' method to set custom headers in the request.
Ensure that the headers are correctly set by inspecting the response.

RestAssured
.given()
.header("CustomHeader", "headerValue")
.when()
.get("https://api.example.com/custom-header-endpoint")
.then()
.statusCode(200)
.header("ResponseHeader", "expectedValue");

33. What is Rest Assured’s ‘with()‘ method, and how can it be used to enhance API testing?

Answer: Rest Assured’s ‘with()‘ method allows you to configure and enhance Rest Assured’s behavior by providing various options and settings. You can use it to specify configurations such as authentication schemes, custom filters, and more to tailor Rest Assured’s behavior to your specific testing needs.

RestAssured
.with()
.authentication(authScheme) // Configure authentication scheme
.filter(requestFilter) // Apply a custom request filter
.get("https://api.example.com/resource")
.then()
.statusCode(200);

34. Explain how you can perform API testing for endpoints that require sending form data in Rest Assured requests.

Answer: To perform API testing for endpoints that require sending form data in Rest Assured requests:

Use the ‘formParam()‘ method to set form parameters in the request.
Ensure that the form parameters are correctly sent and processed by the API.

RestAssured
.given()
.formParam("param1", "value1")
.formParam("param2", "value2")
.when()
.post("https://api.example.com/form-endpoint")
.then()
.statusCode(200);

35. How do you handle testing scenarios that involve validating response time and performance in Rest Assured?

Answer: To handle testing scenarios that involve validating response time and performance in Rest Assured:

Use Rest Assured’s timing assertions, such as ‘time()‘ and ‘timeIn()‘, to measure response times.
Set acceptable response time thresholds and validate that the actual response times meet these thresholds.

RestAssured
.given()
.when()
.get("https://api.example.com/resource")
.then()
.statusCode(200)
.time(lessThan(5000)); // Ensure response time is less than 5 seconds

36. What is the purpose of Rest Assured’s 'filter()' method, and how can it be used to customize API requests and responses?

Answer: Rest Assured’s ‘filter()‘ method is used to apply custom filters to API requests and responses. Filters allow you to customize and manipulate requests and responses at various stages of the HTTP interaction, such as before sending the request or after receiving the response. This is valuable for tasks like logging, modifying headers, or handling specific scenarios (e.g., authentication).

RestAssured
.given()
.filter(requestFilter) // Apply a custom request filter
.when()
.get("https://api.example.com/resource")
.then()
.statusCode(200);

37. How do you handle API testing scenarios that involve working with XML responses in Rest Assured?

Answer: To handle API testing scenarios involving XML responses in Rest Assured:

Set the ‘Content-Type‘ header to specify that the request expects XML responses.
Use XML-specific validation methods and assertions provided by Rest Assured to validate XML content and structure.

RestAssured
.given()
.contentType(ContentType.XML)
.when()
.get("https://api.example.com/xml-endpoint")
.then()
.statusCode(200)
.body("rootElement.childElement", equalTo("expectedValue"));

38. Explain how you can perform API testing for endpoints that require sending binary data (e.g., file uploads) in Rest Assured requests.

Answer: To perform API testing for endpoints that require sending binary data (e.g., file uploads) in Rest Assured requests:

Use the ‘multiPart()‘ method to attach binary files to the request.
Ensure that the file is correctly attached and processed by the API.

import io.restassured.RestAssured;
import io.restassured.http.ContentType;                                                                                                                                     RestAssured
.given()
.multiPart("fileParamName", new File("path/to/file.pdf"), ContentType.PDF)
.when()
.post("https://api.example.com/upload-endpoint")
.then()
.statusCode(200);

39. How can you handle API testing scenarios that involve sending and validating request payloads with nested JSON structures in Rest Assured?

Answer: To handle API testing scenarios with nested JSON payloads in Rest Assured:

Build a nested JSON object or structure in your test code.
Use the ‘body()‘ method to set the JSON payload in the request.
Validate the response using JSON path expressions to access and assert values within the nested structure.

import io.restassured.RestAssured;                                                                                                                                         String requestBody = "{" +
"\"key1\": \"value1\"," +
"\"key2\": {" +
"\"nestedKey\": \"nestedValue\"" +
"}" +
"}";                                                                                                                                                                                                                                                    RestAssured
.given()
.contentType(ContentType.JSON)
.body(requestBody)
.when()
.post("https://api.example.com/json-endpoint")
.then()
.statusCode(200)
.body("key2.nestedKey", equalTo("nestedValue"));

40. What is Rest Assured’s support for handling timeouts, and how can you specify timeout settings for API requests?

Answer: Rest Assured allows you to specify timeout settings for API requests using the ‘timeout()‘ method. You can set the maximum time allowed for a request to complete, both for connecting to the server and for receiving a response. This is important for ensuring that tests do not hang indefinitely due to slow responses.

RestAssured
.given()
.timeout(5000) // Set a timeout of 5 seconds for the request
.when()
.get("https://api.example.com/resource")
.then()
.statusCode(200);

Conclusion

Rest Assured API testing interview questions and answers should further strengthen your knowledge in this domain. Keep in mind that practical experience and hands-on testing with real APIs are essential for mastering Rest Assured and excelling in API testing interviews. Good luck with your preparations!