API Automation with Rest Assured

Validating Response Codes & Body

Learning Outcome

Understand the importance of API response validation

Verify HTTP status codes using Rest Assured

Validate response bodies using string matching and JSON Path

Apply assertions to ensure correct API behavior

Without validation, tests are meaningless. Validation ensures correctness, reliability, and confidence in APIs.

When an API request is executed, receiving a response from the server is not enough.

Testers must verify whether the response is correct, complete, and meets the expected requirements.

Without validation, tests are meaningless. Validation ensures correctness, reliability, and confidence in APIs.

Response validation ensures that the API behaves as expected and returns accurate data to the client application.

It helps detect issues such as incorrect status codes, missing fields, invalid data formats, or unexpected responses.

What Can Be Validated in Rest Assured

Rest Assured allows testers to validate different parts of the API response, such as:

Response Body – Verifies that the returned data contains expected values

Headers – Checks metadata information like authentication tokens or server details.

Content Type – Confirms the response format (e.g., JSON, XML).

Status code – Ensures the API request was processed successfully (e.g., 200, 201).

What to validate

Status Code

Indicates the result of an API request

Confirms whether request was successful or failed

This is the first level of validation

Quickly tells if request succeeded or failed

Status code alone is not enough

Examples :

200 → Success

201 → Created

400 → Bad Request

404 → Not Found

500 → Server Error

Status Code

Contains actual data returned by the API

Used to verify business logic and correctness

Can validate:
- Specific fields (e.g., name, id)
- Values and formats
- Nested JSON structures

This is the most critical part, Even if status is 200, data can be wrong

Always validate important fields and values

Headers

Provide metadata about the response

Used for validation of:
- Authorization details
- Caching information
- Server and response behavior

These carry additional information

Useful in advanced scenarios like auth, caching

Content Type

Defines the format of the response

Ensures API returns expected data type

Common types:
- application/json
- application/xml
- text/html

Prevents issues when parsing response

Response Time

Measures how fast the API responds

Important for performance testing

Helps ensure API meets SLA requirements

Slow APIs can still be “correct” but not usable

Response Time

Think of API validation like ordering food —

Status code tells you the order arrived,

But response body tells you if it’s the correct dish.”

Asserting HTTP status code

Validating simple JSON Response

Validation using jsonPath()

JSON Path is a syntax used to navigate and extract data from a JSON response

It helps access specific fields, values, and nested elements easily

Accessing Values Using JSON Pathg

data.id → 101
data.user.name → John
data.user.age → 30

JSON Path is like addressing system for JSON data

Very useful when working with complex API responses

It allows us to go directly to the required field

(Public API)

How JSON Path is Used in Validation

Used inside .body() method to validate response fields

Helps verify specific values in API response

Example :

.then().body("data.user.name", equalTo("John"));

What happens here ??

Navigates to → data.user.name

Extracts value → "John"

Compares with expected value using equalTo()

Advanced Usage Examples

1 . Validate List Value

.then().body("users[0].name", equalTo("John"));

2 . Validate Multiple Values

.then()

.body("data.id", equalTo(101))

.body("data.user.age", equalTo(30));

Handles nested JSON easily

Why JSON Path is important

Makes validation clean and readable

Reduces complexity in API tests

Using jsonPath() for Nested Values

Response response = given()
.baseUrl("https://api.example.com")
.when()
.get("/user/details");
String city = response.jsonPath().getString("address.city");
System.out.println("City: " + city);

JSON Path is like Google Maps for your API response —

it takes you exactly where your data is.”

What is Extracting Response Data ??

Process of retrieving specific values from API response

Stored in variables for reuse in test automation

Enables dynamic and real-time testing

Why is it important ??

APIs often return dynamic data (IDs, tokens, etc.)

Hardcoding values is not reliable

Helps in:

Setup and Configuration for REST Assured

Build and Validate Project

Maven will automatically download dependencies.

Check External/Referenced Libraries in your IDE

Setup and Configuration for REST Assured

Build and Validate Project

Execute a simple test to confirm proper setup.

Choosing Between TestNG and JUnit

Recommended Project Structure

Contains actual test classes with API verifications.

Shared setup and configuration classes.

Recommended Project Structure

Helper classes for JSON parsing and token generation.

Best Practices for Setup

Base Configuration

public class BaseClass {

    private URI uri;
    private HttpHeaders headers;

    public void setUri(URI uri) {
        this.uri = uri;
    }

    public void setHeaders(HttpHeaders headers) {
        this.headers = headers;
    }
}{{auth_token}}

Keep base URI and common headers in a shared base class. This centralizes common settings.

Best Practices for Setup

Environment Properties

# API testing configuration
# Environment variables
# Base URL
# timeout = $TIMEOUT

base_url = ${BASE_URL}
api_key  = ${API_KEY}
timeout  = ${TIMEOUT}

Use properties files for environment-specific configs. Enables easy switching between test environments.

Best Practices for Setup

Modular Design

public class ModularTestSteps {

    WebDriver driver = new ChromeDriver();

    public void test() {
        driver.get("https://example.com");
        assertThat(driver.getTitle(), equalTo("Example Domain"));
    }
}

Create reusable test components. Use Hamcrest for readable assertions.

Summary

Manual testing is useful for quick checks,automation suits large-scale testing

Tools like Rest Assured simplify and enhance API test automation

API Automation ensures faster and reliable testing

API testing validates system communication and data accuracy

Quiz

Which of the following is a benefit of API automation?

A. Slower execution

B. Requires more manual effort

C. Faster and repeatable testing

D. Only used for UI testing

Quiz-Answer

Which of the following is a benefit of API automation?

A. Slower execution

B. Requires more manual effort

D. Only used for UI testing

C. Faster and repeatable testing