Playwright API Testing

01What is API testing with Playwright

API testing means hitting a service's HTTP endpoints directly - no browser, no DOM. You POST JSON, GET resources, assert status codes, validate response shapes, then move on. Playwright happens to ship an excellent HTTP client called the request fixture. It is built on the same network stack as the browser context, so cookies, proxies, and certificates work uniformly across your UI and API specs.

Why use Playwright instead of Postman or REST Assured?

Three reasons most teams give up Postman collections and Java REST Assured suites for Playwright once they have one Playwright project running:

• Same runner, same reporter. API and UI tests show up in the same HTML report. CI does not need a second runner.
• Same language. If your team writes TypeScript for the UI, they write TypeScript for the API. No context switch to a JSON GUI or Java DSL.
• Trace viewer applies. Every API call shows up in the trace timeline with request body, response body, and headers. Postman has no equivalent.

flowchart LR
  TEST[Playwright test file] --> REQ[request fixture]
  REQ --> CTX[APIRequestContext]
  CTX --> NET[HTTP stack]
  NET --> API[Target REST API]
  API -.JSON.-> NET
  NET -.parsed.-> CTX
  CTX -.Response.-> TEST
  TEST --> EXP[expect assertions]

sequenceDiagram
  participant T as test('book a stay')
  participant R as request
  participant API as restful-booker
  T->>R: POST /auth { username, password }
  R->>API: HTTP POST
  API-->>R: 200 { token: 'abc123' }
  R-->>T: response
  T->>R: POST /booking + Authorization: Bearer abc123
  R->>API: HTTP POST
  API-->>R: 200 { bookingid, booking }
  R-->>T: response
  T->>R: GET /booking/{id}
  R->>API: HTTP GET
  API-->>R: 200 { booking }
  R-->>T: response
  Note over T: assertion: response.json().firstname === 'Pramod'

02The three lectures

Each lecture builds on the last. Lecture 1 teaches the request fixture itself. Lecture 2 adds authentication strategies and schema validation. Lecture 3 inverts the direction - intercepting the browser's network traffic instead of making the calls ourselves.

03Clone the framework

Every code snippet in these lectures lives in a real, runnable Playwright framework. The dedicated branch api-testing-pw ships with the booking client, the OAuth2 token helper, AJV schemas, HAR fixtures, and a small CI workflow.

git clone --branch api-testing-pw https://github.com/PramodDutta/Advance-Playwright-Framework.git
cd Advance-Playwright-Framework
npm install
npx playwright test --project=api

04The API testing pyramid

Most teams over-invest in UI tests and under-invest in API tests. The classic Mike Cohn pyramid still holds: unit at the base, integration / API in the middle, full UI at the top. API tests run 10-100x faster than UI tests and are far less flaky.

05Minimal setup

Three files. That's the whole footprint.

package.json

{
  "name": "pw-api",
  "scripts": { "test": "playwright test" },
  "devDependencies": {
    "@playwright/test": "^1.49.0",
    "ajv": "^8.17.1",
    "ajv-formats": "^3.0.1"
  }
}

playwright.config.ts

import { defineConfig } from '@playwright/test';

export default defineConfig({
  timeout: 30_000,
  use: {
    baseURL: 'https://restful-booker.herokuapp.com',
    extraHTTPHeaders: { 'Accept': 'application/json' },
  },
  projects: [
    { name: 'api', testMatch: /.*\.api\.spec\.ts/ },
  ],
});

tests/booking.api.spec.ts

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

test('ping the heartbeat endpoint', async ({ request }) => {
  const res = await request.get('/ping');
  expect(res.status()).toBe(201);
});

That's the entire shape. Lecture 1 builds the full booking flow on top of this.

DDrills - hub orientation

1. Read the request fixture API reference. Open the official Playwright docs page for APIRequestContext. List the eight methods it exposes (get / post / put / patch / delete / head / fetch / dispose).
2. Confirm reachability. From your local machine, run curl https://restful-booker.herokuapp.com/ping -v and confirm the server returns HTTP/1.1 201 Created. If you see a TLS error, your corporate network proxy is blocking it - hop onto a personal connection.
3. Clone the framework. Follow the clone block above, switch to branch api-testing-pw, run npm install, and run npx playwright test --project=api --list. Confirm at least 12 tests are discovered.
4. Pick your lecture order. Read the lecture cards above. Most students start with CRUD and finish with Network. If your project today is mocking responses, jump straight to Network.

SSolution - minimal smoke test in three languages

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

test('ping returns 201', async ({ request }) => {
  const res = await request.get('https://restful-booker.herokuapp.com/ping');
  expect(res.status()).toBe(201);
});

import com.microsoft.playwright.*;
import static org.junit.jupiter.api.Assertions.*;

public class PingTest {
  public static void main(String[] args) {
    try (Playwright pw = Playwright.create()) {
      APIRequestContext req = pw.request().newContext();
      APIResponse res = req.get("https://restful-booker.herokuapp.com/ping");
      assertEquals(201, res.status());
    }
  }
}

from playwright.sync_api import APIRequestContext, sync_playwright

def test_ping():
  with sync_playwright() as pw:
    req: APIRequestContext = pw.request.new_context()
    res = req.get("https://restful-booker.herokuapp.com/ping")
    assert res.status == 201