How to test Preemptive Authentication in Rest Assured

  

What is Preemptive Authentication?

In preemptive authentication, the client sends the credentials (username & password) in the very first request, rather than waiting for the server to challenge it (with a 401 unauthorized response).

This can improve performance by skipping an extra request-response cycle.

To use preemptive basic auth in Rest Assured:

• Use .auth().preemptive().basic(username, password)

• This sends the Authorization header directly with the GET request.

• You can validate response data with assertions.

API to be tested:

https://postman-echo.com/basic-auth

This endpoint requires Basic Authentication

Username: "postman"

Password: "password"

Java Code using Rest Assured:

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

import static io.restassured.RestAssured.*;
import static org.hamcrest.Matchers.*;

public class PreemptiveAuthTest {

    public static void main(String[] args) {

        // Base URI
        RestAssured.baseURI = "https://postman-echo.com";

        // Preemptive Basic Auth GET Request
        given()
            .auth().preemptive().basic("postman", "password")
        .when()
            .get("/basic-auth")
        .then()
            .statusCode(200)
            .body("authenticated", equalTo(true))
            .log().all();
    }
}

Output:

{
  "authenticated": true
}

Explanation:

Line	Purpose
.auth().preemptive().basic(...)	Sends credentials proactively without waiting for a challenge
.get("/basic-auth")	Executes the GET request
.statusCode(200)	Asserts the response status is OK
.body("authenticated", equalTo(true))	Asserts that authentication was successful
.log().all()	Logs full response details to console

How to test Basic Authentication by using Rest Assured

 

To use Basic Authentication in a GET API via Rest Assured, you need to include the username and password using .auth().basic(username, password) in your request.

What is Basic Authentication?

Basic Auth is an authentication method where:

• The client sends the username and password encoded in Base64 in the request headers.

• The format is:

Authorization: Basic Base64(username:password)

API to be tested:

https://postman-echo.com/basic-auth
It requires:

Username: postman

Password: password

Maven Dependency:

<dependency>
    <groupId>io.rest-assured</groupId>
    <artifactId>rest-assured</artifactId>
    <version>5.3.0</version>
    <scope>test</scope>
</dependency>

Full Java Code

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

import static io.restassured.RestAssured.*;
import static org.hamcrest.Matchers.*;

public class BasicAuthGetAPI {

    public static void main(String[] args) {
        // Set Base URI
        RestAssured.baseURI = "https://postman-echo.com";

        // Send GET request with basic auth
        Response response = given()
                .auth().basic("postman", "password") // Basic Auth
        .when()
                .get("/basic-auth") // GET Endpoint
        .then()
                .statusCode(200) // Check status code
                .body("authenticated", equalTo(true)) // Validate response body
                .extract().response();

        // Print the response
        System.out.println("Response:\n" + response.prettyPrint());
    }
}

Output:

{
  "authenticated": true
}

Code Explanation:

Line	Purpose
.auth().basic("postman", "password")	Adds Basic Auth credentials
.get("/basic-auth")	Performs GET request
.statusCode(200)	Asserts HTTP response is OK
.body("authenticated", equalTo(true))	Asserts authenticated key is true