Writing Your First Test

Now that your environment is set up and you understand RESTful APIs, let's write your first REST Assured test! We'll start with a simple GET request to fetch data from an API.

What is a GET Request?

A GET request is used to retrieve information from a server. For example:

• Getting user details.
• Fetching a list of products.
• Viewing order history.

What Will We Do in This Test?

We will:

• Send a GET request to a Book Library API.
• Check if the response status is 200 (OK).
• Print the response to the console.

We will use the free Book Library API, which provides fake data for testing.

API Endpoint:

This will return details of the book with ISBN 20250401.

Step 1: Create a New Java Class

and create a new class called:

Step 2: Write the GET Request Test

Add the following code to your class:

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

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

public class FirstRestAssuredTest {

    public static void main(String[] args) {

        // Set the base URL for the API
        RestAssured.baseURI = "http://192.xxx.xx.xxx:8080";

        // Send a GET request and store the response
        Response response = given()
                                .when()
                                .get("/books/20250401");

        // Print the response body
        System.out.println("Response: " + response.getBody().asString());

        // Validate the response status code is 200 (OK)
        response.then().statusCode(200);
        System.out.println("Test Passed: Status Code is 200");
    }
}

Step 3: Run the Test

1. Right-click on the FirstRestAssuredTest class.
2. Select Run 'FirstRestAssuredTest'.

If everything is set up correctly, you should see output like this:

Congratulations! You just wrote and ran your first REST Assured test.

Understanding the Code

Let's break down the code step by step:

1. Set the Base URL

This tells REST Assured which API to interact with.

2. Send the GET Request

• given() – Prepares the request (you can add headers, query parameters, etc.).
• when() – Tells REST Assured to send the request.
• get("/books/20250401") – Sends a GET request to the /books/20250401 endpoint.

3. Print the Response

This prints the response body (the data returned by the API).

4. Validate the Status Code

This checks if the status code is 200 (OK). If not, the test will fail.

Step 4: Add More Validations

Let's improve the test by checking specific fields in the response.

Update your test with these extra assertions:

response.then()
        .statusCode(200)                       // Check status code
        .body("isbn", equalTo(20250401))                // Check Book ISBN
        .body("name", equalTo("Book 1"))// Check Book name
        .body("publisher", containsString("ABC")); // Check part of the Publisher

If the validation fails, REST Assured will show an error.

Step 5: Handling Errors Gracefully

If the API is incorrect or unavailable, REST Assured will fail the test.

For example, testing an invalid book:

Response invalidBook = given().when().get("/books/123");
invalidBook.then().statusCode(404); // book not found