Playwright E2e Testing

Playwright E2E Testing (TypeScript)

Comprehensive toolkit for end-to-end testing of web applications using Playwright with TypeScript. Enables robust UI testing, UI-dependent API setup, and responsive design verification following best practices.

Activation: This skill is triggered when authoring or maintaining versioned Playwright UI specs and their test infrastructure.

When to Use This Skill

• Write E2E tests for user flows, forms, navigation, and authentication
• UI-dependent API setup via the request fixture or network interception
• Responsive testing across mobile, tablet, and desktop viewports
• Debug flaky tests using traces, screenshots, videos, and Playwright Inspector
• Setup test infrastructure with Page Object Model and fixtures
• Mock/intercept APIs for isolated, deterministic testing
• Visual regression testing with screenshot comparisons

Do NOT Use For

• Standalone API/contract testing with no browser (use api-testing).
• Driving a live browser interactively for exploration or debugging (use playwright-cli).
• Governing a large regression suite, tiers, or CI sharding strategy (use playwright-regression-testing).
• Selenium/Java browser automation (use webapp-selenium-testing).

Prerequisites

Quick Setup

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# Initialize new project
npm init playwright@latest

# Or add to existing project
npm install -D @playwright/test
npx playwright install

First Questions to Ask

Before writing tests, clarify:

1. App URL: Local dev server command + port, or staging URL?
2. Critical flows: Which user journeys must be covered (happy path + error states)?
3. Browsers/devices: Chrome, Firefox, Safari? Mobile viewports?
4. API strategy: Real backend, mocked responses, or hybrid?
5. Test data: Seed data available? Reset/cleanup strategy?

Core Principles

1. Test Runner & TypeScript

Always use @playwright/test with TypeScript for type safety and better IDE support.

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

test("user can login", async ({ page }) => {
  await page.goto("/login");
  await page.getByLabel("Email").fill("user@test.com");
  await page.getByLabel("Password").fill("password123");
  await page.getByRole("button", { name: "Sign in" }).click();
  await expect(page).toHaveURL(/.*dashboard/);
});

2. Locator Strategy (Priority Order)

Prefer role-based locators (getByRole) with accessible names, then label → placeholder → text → test ID → CSS (last resort). XPath is never used.

➡️ Full priority hierarchy, role reference, and examples: Locator Strategies: Priority — the single source of truth.

3. Auto-Waiting & Web-First Assertions

Playwright auto-waits for elements. Never use sleep() or arbitrary timeouts.

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// [ok] Web-first assertions (auto-retry)
await expect(page.getByRole("alert")).toBeVisible();
await expect(page).toHaveURL(/dashboard/);
await expect(page.getByTestId("status")).toHaveText("Success!");

// [no] Avoid manual waits
await page.waitForTimeout(2000); // Bad practice

4. Test Structure with Steps

Use test.step() for readable reports and failure localization:

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test("checkout flow", async ({ page }) => {
  await test.step("Add item to cart", async () => {
    await page.goto("/products/1");
    await page.getByRole("button", { name: "Add to Cart" }).click();
  });

  await test.step("Complete checkout", async () => {
    await page.goto("/checkout");
    await page.getByRole("button", { name: "Pay Now" }).click();
  });

  await test.step("Verify confirmation", async () => {
    await expect(page.getByRole("heading")).toContainText("Order Confirmed");
  });
});

Key Workflows

Forms & Navigation

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// Form submit and wait for navigation (auto-waiting)
await page.getByRole("button", { name: "Login" }).click();
await expect(page).toHaveURL(/.*dashboard/);

// Form with API response validation
const responsePromise = page.waitForResponse(
  (r) => r.url().includes("/api/login") && r.status() === 200,
);
await page.getByRole("button", { name: "Login" }).click();
const response = await responsePromise;

API Testing (Request Fixture)

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test("API health check", async ({ request }) => {
  const response = await request.get("/api/health");
  expect(response.ok()).toBeTruthy();
  expect(await response.json()).toMatchObject({ status: "ok" });
});

API Mocking & Interception

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test("handles API error", async ({ page }) => {
  await page.route("**/api/users", (route) =>
    route.fulfill({
      status: 500,
      body: JSON.stringify({ error: "Server error" }),
    }),
  );
  await page.goto("/users");
  await expect(page.getByRole("alert")).toContainText("Something went wrong");
});

Responsive Testing

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const viewports = [
  { width: 375, height: 667, name: "mobile" },
  { width: 768, height: 1024, name: "tablet" },
  { width: 1280, height: 720, name: "desktop" },
];

for (const vp of viewports) {
  test(`navigation works on ${vp.name}`, async ({ page }) => {
    await page.setViewportSize(vp);
    await page.goto("/");
    // Mobile: hamburger menu
    if (vp.width < 768) {
      await page.getByRole("button", { name: /menu/i }).click();
    }
    await page.getByRole("link", { name: "About" }).click();
    await expect(page).toHaveURL(/about/);
  });
}

Configuration

Use playwright.config.ts for project-wide settings:

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import { defineConfig, devices } from "@playwright/test";

export default defineConfig({
  testDir: "./tests",
  retries: process.env.CI ? 2 : 0,
  reporter: [["html"], ["junit", { outputFile: "results.xml" }]],
  use: {
    baseURL: "http://localhost:3000",
    trace: "on-first-retry",
    screenshot: "only-on-failure",
    video: "retain-on-failure",
  },
  projects: [
    { name: "chromium", use: devices["Desktop Chrome"] },
    { name: "mobile", use: devices["Pixel 5"] },
  ],
  webServer: {
    command: "npm run dev",
    url: "http://localhost:3000",
    reuseExistingServer: !process.env.CI,
  },
});

Troubleshooting

CLI Quick Reference

Red Flags

• CSS/XPath locators when a role/label/testId is available — brittle and breaks on refactor.
• waitForTimeout / manual sleeps instead of web-first auto-retrying assertions.
• Tests sharing state and depending on execution order — flaky and order-coupled.
• Assertions only on status/URL with no visible-state check — hides render regressions.
• Inline page setup repeated across tests instead of fixtures — duplication and drift.

References

Verification

• Uses custom fixture injection — No new PageObject() calls in spec files; all POMs injected via fixtures
• Locators use recommended strategies — All locators use getByRole(), getByTestId(), or getByText(); no CSS selectors for interactive elements
• Tests are independent — Each test sets up and tears down its own state; no beforeAll with shared mutable state
• Error states covered — At least one test verifies error/empty/loading states alongside happy path