D. E. Shaw Playwright Testing Interview Questions & Answers

A short function syntax that does not have its own this and arguments, taking them from the surrounding scope.

Cover happy path, validation errors, auth and permissions, boundary values, idempotency, schema, performance and data cleanup.

beforeEach runs the same code before every test in scope; fixtures are lazy, composable and only set up what a test uses.

User-facing ones: getByRole, getByText, getByLabel, getByPlaceholder and getByTestId, which are more resilient than CSS or XPath.

Register page.on('dialog', d => d.accept()) before the action triggers the dialog.

Use environment variables or .env files, a baseURL in config, API calls for setup and cleanup, and unique data per run.

Use device descriptors such as devices['iPhone 13'] in a project config to emulate viewport, user agent and touch.

A type alias describes a shape or union of values; an enum creates a named set of constants that exists at runtime.

waitForSelector is a lower-level wait; locator assertions are preferred as they retry and are more readable.

Tag tests (in the title or with { tag: '@smoke' }) and run: npx playwright test --grep @smoke (use --grep-invert to exclude).

Playwright supports multiple browsers, tabs, languages and has auto-waiting and tracing; Selenium has the widest ecosystem; Cypress runs in-browser with a great UI but has more limits across tabs.

Both describe object shapes. Interfaces can be extended and merged; type aliases can also describe unions and primitives. Use interfaces for page or test-data shapes, types for unions.

API testing checks services directly and is fast and stable; UI testing checks the full user experience in the browser and is slower.

Separate tests, page objects, fixtures, utilities, test data and config; use tags, projects, shared auth setup, linting, code review and a CI pipeline with sharding and reports.

Wait for the popup event with const [popup] = await Promise.all([page.waitForEvent('popup'), page.click('a')]), then interact with popup.

Send invalid payloads or missing auth and assert 400, 401 or 404 codes and the error message bodies.

npx playwright test tests/login.spec.ts, add -g "test title" to match a name, or use test.only while debugging.

Use expect(page).toHaveScreenshot() to compare with stored baselines, with thresholds and masks for dynamic regions.

npx playwright codegen records user actions and generates test code with suggested locators, handy for starting tests.

Turn on trace: 'on-first-retry', open the trace viewer, check network and timing, replace hard waits with web-first assertions, isolate test data and check for sharding conflicts.

click simulates a real user click with actionability checks; dispatchEvent fires a DOM event directly without those checks.

Use page.waitForResponse(res => res.url().includes('/api/orders') && res.ok()) together with the action that triggers it.

Record timestamps around the request or use response timing, then assert the duration is under an agreed threshold.

JavaScript runs one call stack and uses queues for async work; the event loop pushes callbacks from the microtask (promises) and task queues when the stack is empty.

Define an interface for the payload, cast or validate the parsed JSON to it (for example with zod), and use that type in assertions to catch shape changes.

await expect(page).toHaveScreenshot('home.png') compares against a baseline image; tune maxDiffPixels and mask dynamic areas like dates.

Log in once in global setup, save storageState to a JSON file and set use.storageState in the config so every test starts logged in.

Both describe the shape of data. Interfaces are extendable and suit object contracts; type aliases can also model unions and primitives.

Define projects for chromium, firefox and webkit in playwright.config.ts, set workers, then run: npx playwright test

Reusable setup/teardown units injected into tests (page, context, request). You can extend test with custom fixtures such as loggedInPage.

Destructuring pulls values from arrays or objects into variables; spread expands an array or object into another, useful for copying and merging config.

Strings in backticks that allow embedded expressions like `Hello ${name}` and multi-line text, useful for building dynamic locators and URLs.

Rely on auto-waiting plus a web-first assertion on the final state, disable animations in config for tests and avoid fixed timeouts.

locator.hover() and locator.dragTo(target) perform these actions, with auto-waiting for actionability.

Install the allure-playwright reporter, add it in the config reporters array and generate the report from the allure-results folder in CI.

Functions that take other functions as arguments or return them, such as map, filter and reduce, or a helper that wraps retry logic around a test step.

Log in with request.post, call request.storageState(), and create a browser context using that state.

Use the official Playwright image which contains browsers and dependencies, mount the project and run npx playwright test for consistent CI environments.

Capture the download event, save it with download.saveAs, then read the file in Node and assert on name, size or content.

Workflow: checkout → setup-node → npm ci → npx playwright install --with-deps → npx playwright test → upload playwright-report as an artifact.

Fetch tokens in a fixture with expiry tracking and refresh it when it is about to expire, keeping tests unaware of the details.

Use page.route to intercept the call and fulfil it with fixed JSON so tests do not depend on external systems.

Use page.frameLocator('#frame').getByRole(...) so actions work inside the iframe with auto-waiting.

Use npx playwright test --shard=1/4 in each CI job and merge reports afterwards to reduce total run time.

Integrate axe-core through @axe-core/playwright, run an analysis on the page and assert that there are no violations.

Fixtures set up and tear down test dependencies. Extend with test.extend({ loggedInPage: async ({ page }, use) => { ...; await use(page); } }).

page.route('**/api/items', route => route.fulfill({ json: [...] })) intercepts and replies with test data; route.abort() simulates failures.

npm is the Node package manager. package.json lists the project's dependencies and scripts, such as the command that runs the tests.

setInputFiles on the input for uploads; for downloads wait on page.waitForEvent('download') and save or inspect the file.

page.screenshot() for captures and config options use: { screenshot: 'only-on-failure', video: 'retain-on-failure' } for automatic evidence.

test.step groups actions into named steps in reports; annotations such as test.skip, test.fixme and test.slow communicate intent and adjust behaviour.

Use --debug or the Inspector, page.pause(), UI mode, the trace viewer and headed runs with slowMo.

string, number, boolean, null, undefined, symbol, bigint and object (including arrays and functions).

List, dot, line, HTML, JSON and JUnit reporters, plus integrations such as Allure, configurable per environment.

const [newPage] = await Promise.all([ context.waitForEvent('page'), page.getByText('Open').click(), ]); await newPage.waitForLoadState();

Create test data through API calls, verify it in the UI and clean up via API, which makes UI tests faster and more reliable.

Set retries in the config or CLI and failed tests re-run in a fresh context, with trace recorded on first retry to diagnose flakiness.

A function that remembers variables from its outer scope even after that scope has finished. They are used for private state and factory helpers.

Named configurations that run the same tests across different browsers, devices or environments.

A Locator is lazy, re-resolved on every action and auto-waits (recommended). An ElementHandle points to one DOM node and can go stale.

await page.route('**/api/users', route => route.fulfill({ status: 200, json: [{ id: 1, name: 'Test' }] }) );

Scripts that run once before or after the whole run, for seeding data, starting services or creating authentication state.

Add tags in the title (@smoke) or use the tag option, and run with --grep @smoke or --grep-invert.

Use timeout and expect.timeout in config, test.setTimeout() for one test and test.slow() for known slower tests.

A browser is the engine instance; a context is an isolated session (cookies, storage); a page is a tab inside a context.

An open-source end-to-end testing framework from Microsoft that automates Chromium, Firefox and WebKit through one API, in multiple languages.

In a fixture or beforeEach, call the API (request.post) to create the user or order, use it in the UI test, then delete it in teardown. It is faster and more reliable than creating data through the UI.

Create a class that takes a page, defines locators as properties and exposes action methods; instantiate it in a fixture for clean tests.

Set them in the context options (geolocation, permissions, timezoneId, locale) to simulate users from other regions.

await expect.soft(locator).toHaveText('...') records the failure but lets the test continue, so you see every mismatch in one run.

Syntax over Promises: an async function returns a Promise and await pauses until it resolves. Every Playwright action returns a Promise, so you await each step.

Use a library such as zod or ajv to define the expected schema and parse the response to fail on missing or wrongly typed fields.