Tutorials123: Automation Testing Tutorial

What is response header in API?

A response header in an API is metadata returned by the server along with the body of the response. It provides additional information about the response, such as:

Content-Type → tells the format of the response (e.g., application/json, text/html).
Content-Length → specifies the size of the response body.
Server → identifies the server software handling the request.
Cache-Control → gives caching directives to the client.
Set-Cookie → passes cookies from server to client.

These headers don’t contain the main data (which is usually in the response body), but they are critical for understanding how to interpret and handle the response.

When testing with Rest Assured, you usually verify that:

1. The response contains a specific header

Example: Check if the header Content-Type is present.

2. The header has the expected value

Example: Verify that Content-Type equals application/json.

3. The header value matches certain conditions

Example: Check if the value starts with application/.

In Rest Assured, testing a single response header means making an API request, capturing the response, and then asserting the value of that particular header against the expected outcome.

We want to:

Send a GET request to https://reqres.in/api/users?page=2
Extract and validate a specific response header (example: Content-Type)

Below is the screenshot of response of API: https://reqres.in/api/users?page=2

To test a single response header in a GET API using Rest Assured in Java, you can follow these steps:

Set the base URI
Send a GET request
Extract the specific header
Validate it using assertion

Sample Java Code Using Rest Assured

import io.restassured.RestAssured;
import io.restassured.response.Response;

import static org.hamcrest.MatcherAssert.assertThat;
import static org.hamcrest.Matchers.equalTo;

public class GetResponseHeaderTest {

    public static void main(String[] args) {
        
        // Step 1: Set base URI
        RestAssured.baseURI = "https://reqres.in";

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

        // Step 3: Print and verify a single header, e.g. Content-Type
        String contentType = response.getHeader("Content-Type");
        System.out.println("Content-Type header is: " + contentType);

        // Step 4: Assert the header
        assertThat("Header validation failed", contentType, equalTo("application/json; charset=utf-8"));
    }
}

Code explanation:

Set base URI
Send GET request and get response from API
Print a single response header names content type
Assert the response header

Maven Dependency:

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

How to Test a Single Response Header by Rest Assured

To test a single response header in a GET API using Rest Assured in Java, you can follow these steps: