API Testing with Playwright: A Comprehensive Guide

Playwright is widely known for browser automation, it also offers powerful features for API testing, making it a versatile tool for end-to-end testing. By using Playwright, testers can efficiently validate API endpoints, perform authentication checks, and seamlessly integrate API tests with UI tests to ensure consistent functionality across the entire application. API testing with Playwright allows for the testing of various HTTP methods, including GET, POST, PUT, and DELETE requests, enabling comprehensive validation of data flow and business logic. Additionally, Playwright supports handling complex authentication scenarios, such as token-based and OAuth authentication. This guide will explain why Playwright is an excellent choice for API testing, how to set it up and provide detailed examples of requests, authentication handling, and best practices for effective and efficient API testing.

Basics of API Testing

API testing checks if different software systems can communicate and exchange data correctly. It ensures functionality, security, and performance while being faster and easier to automate than UI testing. Unlike UI testing, which focuses on visual elements, API testing verifies the backend logic using requests like GET and POST. It also differs from unit testing, which tests individual functions, and integration testing, which checks how system parts work together.

Why Choose Playwright for API Testing?

API testing is a crucial aspect of software testing, ensuring that backend services function correctly before integrating them with the UI. Several tools are available for API testing, each offering unique features suited to different testing needs:

• Postman – A widely used API testing tool with a graphical interface for sending requests and validating responses.
• RestAssured – A Java-based API testing framework commonly used for automated API validation.
• SoapUI – A dedicated tool for testing SOAP and REST APIs, offering advanced features for functional and security testing.
• SuperTest – A JavaScript library designed for testing HTTP APIs, particularly useful in Node.js applications.
• Cypress – Primarily a UI testing framework that also includes basic API testing capabilities.

Then why should we use Playwright for API testing? It allows users to make API requests, validate responses, and integrate API checks within automated test scripts. It provides features like APIRequestContext for direct API interactions, built-in authentication handling, and cross-browser support, making it a versatile option for teams looking to perform both API and UI testing within the same environment. Like other tools, Playwright offers a structured approach to API testing, enabling efficient validation of backend services. Now let’s take a deeper look at all the key features.

Key Features of Playwright That Enhance API Testing

1. Built-in APIRequestContext for Simplified API Testing

Playwright provides APIRequestContext, allowing testers to make API calls directly within test scripts without needing external libraries like Axios or SuperTest.

Example: GET Request with Playwright

import { test, expect, request } from '@playwright/test';

test('Validate GET request', async ({ request }) => {
    const response = await request.get('https://jsonplaceholder.typicode.com/posts/1');
    expect(response.status()).toBe(200);

    const responseBody = await response.json();
    expect(responseBody.id).toBe(1);
});

Why Playwright? Unlike Postman (which is UI-based) and RestAssured (which requires Java), Playwright allows API requests directly within the test automation framework with minimal setup.

2. Seamless Integration of API & UI Testing

Unlike Postman, RestAssured, and SoapUI, which focus only on API testing, Playwright enables UI and API tests to run in the same framework. This is useful for:

• Setting up test data via API before UI tests.
• Validating API responses against UI elements.
• Testing UI interactions that trigger API calls.

Example: API and UI Test Together

test('Create user via API and validate on UI', async ({ page, request }) => {
    const response = await request.post('https://jsonplaceholder.typicode.com/users', {
        data: { name: 'John Doe', email: '[email protected]' }
    });

    expect(response.status()).toBe(201);
    const user = await response.json();

    await page.goto('https://example.com/users');
    const userExists = await page.locator(`text=${user.name}`).isVisible();
    expect(userExists).toBeTruthy();
});

3. JavaScript/TypeScript Support for Modern Development

Playwright is built for JavaScript and TypeScript, making it ideal for teams using modern web frameworks like React, Angular, and Vue.js.

Comparison with Other Tools:

Why Playwright? Teams using JavaScript for frontend development can now write API tests in the same language, improving efficiency and collaboration.

4. Cross-Browser & Cross-Platform API Testing

Unlike most API testing tools that only test API responses, Playwright supports cross-browser validation, ensuring that API responses work correctly with different browsers.

Example: API Test Across Browsers

import { test, expect, request } from '@playwright/test';

test('Validate API response in different browsers', async ({ browser }) => {
    const context = await browser.newContext();
    const request = context.request;
    const response = await request.get('https://jsonplaceholder.typicode.com/posts/1');
    expect(response.status()).toBe(200);
});

Why Playwright?

• Postman, RestAssured, and SoapUI cannot test how APIs behave across different browsers.
• Playwright ensures API + UI compatibility across Chromium, Firefox, and WebKit (Safari).

5. CI/CD Integration for Automated API Testing

Playwright works seamlessly with CI/CD pipelines, allowing automated API testing in:

• Jenkins
• GitHub Actions
• GitLab CI/CD

Example: Running Playwright API Tests in GitHub Actions

name: Playwright API Tests
on: push

jobs:
  test:
    runs-on: ubuntu-latest
    steps:
      - name: Checkout code
        uses: actions/checkout@v2
      
      - name: Install dependencies
        run: npm install
      
      - name: Run API Tests
        run: npx playwright test api-tests

Why Playwright? Unlike Postman, which requires Newman for automation, Playwright runs API tests directly in CI/CD pipelines without additional setup.

Guide to Writing tour First API Test with Playwright

To get started with API Testing with Playwright, install Playwright using npm:

npm init -y
npm install @playwright/test

Ensure that Playwright is installed by running:

npx playwright install

Writing Your First API Test with Playwright

You can use APIRequestContext to interact with APIs. Below is a simple GET request example:

import { test, expect, request } from '@playwright/test';

test('Validate GET request', async ({ request }) => {
    const response = await request.get('https://jsonplaceholder.typicode.com/posts/1');
    expect(response.status()).toBe(200);

    const responseBody = await response.json();
    expect(responseBody.id).toBe(1);
});

Breaking Down the Code:

• Import Playwright functions: test, expect, and request are used for API testing.
• Make a GET request: request.get() fetches data from the API.
• Validate the response status: Ensures the request was successful (200 OK).
• Parse and validate response body: Converts the response to JSON and checks if the expected data is returned.

Making Different API Requests

1. POST Request (Creating a Resource)

test('Validate POST request', async ({ request }) => {
    const response = await request.post('https://jsonplaceholder.typicode.com/posts', {
        data: {
            title: 'Playwright API Test',
            body: 'This is a test post',
            userId: 1
        }
    });

    expect(response.status()).toBe(201);
    const responseBody = await response.json();
    expect(responseBody.title).toBe('Playwright API Test');
});

• Sends a POST request to create a new resource.
• Validates response status (201 Created) to confirm successful creation.
• Ensures response data matches the expected values.

2. PUT Request (Updating a Resource)

test('Validate PUT request', async ({ request }) => {
    const response = await request.put('https://jsonplaceholder.typicode.com/posts/1', {
        data: {
            id: 1,
            title: 'Updated Title',
            body: 'Updated content',
            userId: 1
        }
    });

    expect(response.status()).toBe(200);
    const responseBody = await response.json();
    expect(responseBody.title).toBe('Updated Title');
});

• Sends a PUT request to update an existing resource.
• Validates status code (200 OK) for successful updates.
• Confirms that the updated title matches the expected value.

3. DELETE Request (Removing a Resource)

test('Validate DELETE request', async ({ request }) => {
    const response = await request.delete('https://jsonplaceholder.typicode.com/posts/1');
    expect(response.status()).toBe(200);
});

• Sends a DELETE request to remove an existing resource.
• Checks if the API returns a successful deletion status (200 OK or 204 No Content).

Handling Authentication in API Testing

For APIs requiring authentication, Playwright supports passing headers and cookies for authorization.

test('Validate Authenticated Request', async ({ request }) => {
    const response = await request.get('https://example.com/protected', {
        headers: {
            Authorization: 'Bearer YOUR_ACCESS_TOKEN'
        }
    });

    expect(response.status()).toBe(200);
});

• Includes Authorization Header: Uses a Bearer token for authentication.
• Validates Authentication: Ensures the API allows access (200 OK).

Best Practices for API Testing with Playwright

To ensure efficient and maintainable API testing with Playwright, it is important to follow structured practices that enhance test reliability, performance, and organization. By properly structuring test suites, managing dependencies, and optimizing execution, teams can achieve faster, more scalable, and maintainable API tests. Below are some key best practices to maximize efficiency:

• Use Fixtures – Helps maintain test reusability and efficiency by providing a structured way to set up and share test data across multiple tests.
• Validate Response Schema – Use schema validation tools like Ajv to ensure API responses follow the expected structure, reducing inconsistencies.
• Use Environment Variables – Store API URLs, authentication tokens, and sensitive data securely using environment variables to enhance security and flexibility.
• Enable Logging – Capture and log API responses to debug test failures efficiently, making troubleshooting easier.
• Run Tests in Parallel – Speed up execution using Playwright’s parallel test execution feature, optimizing test suite performance.

Conclusion

As seen in our blog, Playwright is a powerful tool for both UI automation and API testing, offering seamless integration of API and UI tests within a single framework. With features like built-in request handling, authentication management, parallel execution, and cross-browser compatibility, it simplifies API testing while improving efficiency and reliability. By using Playwright, teams can reduce execution time, automate authentication, organize test suites efficiently, and improve debugging with logging and structured test cases.

For businesses looking to enhance their API testing strategy, Codoid, a leader in software testing services, provides expert API automation solutions. With extensive experience in Playwright, Selenium, and other frameworks, Codoid helps organizations optimize testing processes, improve test coverage, and ensure smooth digital experiences. By adopting Playwright and partnering with Codoid, teams can build a scalable, efficient, and future-ready test automation strategy.

Frequently Asked Questions