Introduction to REST Assured

REST Assured is a Java library that simplifies the testing of REST APIs by providing a domain-specific language (DSL) for writing tests. It allows you to validate responses, check HTTP status codes, and manipulate request headers all in a straightforward, human-readable style. If you're familiar with basic Java programming, diving into REST Assured will feel intuitive.

Setting Up REST Assured

Before we delve into the syntax, ensure that you have the following dependencies included in your project. If you're using Maven for dependency management, add the following to your pom.xml:

<dependency>
    <groupId>io.rest-assured</groupId>
    <artifactId>rest-assured</artifactId>
    <version>4.3.3</version>
    <scope>test</scope>
</dependency>

Don't forget to include your testing framework (like JUnit or TestNG) if you haven't already.

Basic Structure of a REST Assured Test

A simple REST Assured test typically follows this structure:

1. Given – Set up your test data and preconditions.
2. When – Execute the action you want to test (usually an API call).
3. Then – Verify the outcome (check the response).

Example: A Simple GET Request

Let's create a simple GET request to retrieve user information from a hypothetical API.

import io.restassured.RestAssured;
import io.restassured.response.Response;
import org.junit.Test;
import static org.hamcrest.Matchers.*;

public class UserAPITest {
    
    @Test
    public void getUserDetails() {
        // Given
        RestAssured.baseURI = "https://api.example.com";

        // When
        Response response = RestAssured
                .given()
                .pathParam("userId", 1)  // Setting a path parameter
                .when()
                .get("/users/{userId}");

        // Then
        response.then()
                .statusCode(200)  // Validate status code
                .body("name", equalTo("John Doe"))  // Validate response body
                .body("email", containsString("@example.com"));  // More validation
    }
}

Breakdown of the Example

• Given: We set the base URI for the API we want to test. Here, we are using a fictitious example API.
• When: We make a GET request to the /users/{userId} endpoint, specifying the user ID we want in the path.
• Then: We verify that the HTTP response status code is 200, indicating a successful request. Additionally, we validate specific fields in the JSON response body.

Common Methods in REST Assured

Understanding the commonly used methods can streamline your testing process:

Setting Headers

You can easily set headers using the .header() method. For example, to set a Content-Type header:

.given()
    .header("Content-Type", "application/json")

Sending Queries

When sending GET requests, you may also need to add query parameters:

.given()
    .queryParam("page", 1)

Validating Response Content

Bolster your test's validity by checking various response aspects:

• Status Code: statusCode()
• Response Body: body()
• Response Time: time()

Example: Validating Response Time

To check if a response returns within a specified time, you can add:

.response()
    .time(lessThan(2000L)); // Check if response time is less than 2 seconds

Conclusion

In this blog post, we explored the basic syntax and structure of REST Assured for API testing. We've seen how to perform simple GET requests while verifying status codes and validating response contents. REST Assured's fluent syntax allows for clear and concise API testing, making it a favorite among software testers.

With this foundational knowledge, you can begin to explore more advanced features and methodologies REST Assured offers, deepening your understanding of API testing best practices.