How to test API Response by Rest Assured

  

In below example, we are going to test response of API.

This is the API we are going to test: 

https://reqres.in/api/users?page=2

Below are maven dependencies:

<dependencies>
    <dependency>
        <groupId>io.rest-assured</groupId>
        <artifactId>rest-assured</artifactId>
        <version>5.4.0</version>
        <scope>test</scope>
    </dependency>

    <dependency>
        <groupId>org.testng</groupId>
        <artifactId>testng</artifactId>
        <version>7.9.0</version>
        <scope>test</scope>
    </dependency>
</dependencies>

Java Code:

import io.restassured.RestAssured;
import io.restassured.response.Response;
import org.testng.Assert;
import org.testng.annotations.Test;

public class ResponseBodyContainsTest {

    @Test
    public void testResponseBodyContains() {
        // Set the base URI
        RestAssured.baseURI = "https://reqres.in";

        // Send GET request and capture response
        Response response = RestAssured
                .given()
                .when()
                .get("/api/users?page=2")
                .then()
                .statusCode(200) // Validate status code
                .extract()
                .response();

        // Convert response body to String
        String responseBody = response.asString();

        // Print for reference
        System.out.println("Response Body:\n" + responseBody);

        // Use contains() to validate specific strings
        Assert.assertTrue(responseBody.contains("George"), "Expected name not found in response");
        Assert.assertTrue(responseBody.contains("email"), "Expected 'email' field not found in response");
        Assert.assertTrue(responseBody.contains("janet.weaver@reqres.in") == false, "Unexpected email found in response");
    }
}

Important Points:




• .contains() is case-sensitive.

• You can test for presence/absence of any string that should/shouldn't be in the response.

• Prefer this method for quick validations; for structured validations, use JSON path instead.

How to Test Response Headers of API by Rest Assured

To test response headers of a GET API using Rest Assured, follow these steps:

What are response headers?

Response headers are metadata returned by the server. Examples include:

• Content-Type: Describes the type of the response (example: application/json)

• Server: Information about the server

• Date: Time of the response

• Content-Encoding, Connection, etc.

Steps to test response headers using Rest Assured:

• Set Base URI using RestAssured.baseURI
• Send GET Request using given().get(endpoint)
• Extract Headers from the response
• Verify Specific Headers using assertions
  
  

Maven Dependency for Rest Assured

<dependencies>
    <dependency>
        <groupId>io.rest-assured</groupId>
        <artifactId>rest-assured</artifactId>
        <version>5.3.2</version>
        <scope>test</scope>
    </dependency>
</dependencies>

Java Code: Get and Test Response Headers

import io.restassured.RestAssured;
import io.restassured.response.Response;
import io.restassured.http.Headers;
import io.restassured.http.Header;

public class GetResponseHeaders {

    public static void main(String[] args) {

        // Step 1: Set Base URI
        RestAssured.baseURI = "https://reqres.in/api";

        // Step 2: Send GET request
        Response response = RestAssured
                .given()
                .get("/users?page=2");

        // Step 3: Print all headers
        Headers allHeaders = response.getHeaders();
        System.out.println("===== All Response Headers =====");
        for (Header header : allHeaders) {
            System.out.println(header.getName() + ": " + header.getValue());
        }

        // Step 4: Get a specific header
        String contentType = response.getHeader("Content-Type");
        String server = response.getHeader("Server");

        System.out.println("\nContent-Type: " + contentType);
        System.out.println("Server: " + server);

        // Step 5: Validate headers using assertions
        if (!"application/json; charset=utf-8".equals(contentType)) {
            throw new AssertionError("Expected Content-Type not found!");
        }

        if (!"cloudflare".equalsIgnoreCase(server)) {
            throw new AssertionError("Expected Server header value not found!");
        }

        System.out.println("\n Header validations passed successfully!");
    }
}

Output:

===== All Response Headers =====
Date: Mon, 28 Jul 2025 14:00:00 GMT
Content-Type: application/json; charset=utf-8
Transfer-Encoding: chunked
Connection: keep-alive
Server: cloudflare
...

Content-Type: application/json; charset=utf-8
Server: cloudflare

Header validations passed successfully!

Useful Methods in Rest Assured

• response.getHeaders() – Gets all headers

• response.getHeader("Header-Name") – Gets a specific header

• response.header("Header-Name") – Alias for getHeader