E2E testing with Playwright in Svelte

Introduction

E2E testing checks if your whole app works well from a user's view. Playwright helps you do this by controlling a browser to test your app automatically.

You want to make sure clicking buttons and filling forms works as expected.

You need to test your app on different browsers like Chrome and Firefox.

You want to catch bugs before users find them by simulating real user actions.

You want to test navigation between pages in your Svelte app.

You want to check that your app looks and behaves correctly after changes.

Syntax

Svelte

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

test('test name', async ({ page }) => {
  await page.goto('http://localhost:3000');
  await page.click('selector');
  await expect(page.locator('selector')).toHaveText('expected text');
});

Use page.goto(url) to open your app in the browser.

Use page.click(selector) to simulate user clicks.

Examples

This test opens the homepage and checks the page title.

Svelte

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

test('check homepage title', async ({ page }) => {
  await page.goto('http://localhost:3000');
  await expect(page).toHaveTitle('My Svelte App');
});

This test clicks a button and checks if a message appears.

Svelte

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

test('click button and check text', async ({ page }) => {
  await page.goto('http://localhost:3000');
  await page.click('button#submit');
  await expect(page.locator('p#message')).toHaveText('Submitted!');
});

Sample Program

This test opens the Svelte app, clicks a button that increases a counter, and checks if the counter shows '1'.

Svelte

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

test('E2E test for Svelte app button click', async ({ page }) => {
  // Open the app
  await page.goto('http://localhost:3000');

  // Click the button with id 'increment'
  await page.click('button#increment');

  // Check if the counter text updated to '1'
  await expect(page.locator('span#count')).toHaveText('1');
});

Important Notes

Use clear and stable selectors like IDs or data-test attributes for locating elements.

Run your app locally before running Playwright tests to avoid connection errors.

Playwright can test on multiple browsers; specify them in the config for wider coverage.

Summary

E2E testing checks your app from the user's point of view.

Playwright automates browsers to run these tests easily.

Write tests that open pages, interact with elements, and check results.

Practice

1. What is the main purpose of E2E testing with Playwright in a Svelte app?

easy

A. To test the app from the user's point of view by automating browser actions

B. To check only the backend API responses without UI interaction

C. To write unit tests for individual Svelte components

D. To manually test the app by clicking buttons in the browser

Solution

1. Step 1: Understand E2E testing purpose

   E2E testing simulates real user actions to verify the whole app works correctly.

2. Step 2: Role of Playwright in E2E testing

   Playwright automates browsers to perform user-like actions and check results automatically.

3. Final Answer:

   To test the app from the user's point of view by automating browser actions -> Option A

4. Quick Check:

   E2E testing = user perspective automation [OK]

Hint: E2E tests mimic user actions in a real browser [OK]

Common Mistakes:

• Confusing E2E with unit or API testing
• Thinking E2E tests run only backend checks
• Assuming manual testing is E2E automation

2. Which of the following is the correct way to launch a browser and open a page in Playwright for a Svelte app test?

easy

A. const page = await playwright.newPage(); const browser = await page.launch();

B. const page = await browser.launch(); const browser = await playwright.newPage();

C. const browser = playwright.launch(); const page = browser.newPage();

D. const browser = await playwright.chromium.launch(); const page = await browser.newPage();

Solution

1. Step 1: Correct Playwright browser launch syntax

   Playwright requires launching the browser first with await playwright.chromium.launch().

2. Step 2: Creating a new page from the browser

   After launching, create a new page with await browser.newPage().

3. Final Answer:

   const browser = await playwright.chromium.launch(); const page = await browser.newPage(); -> Option D

4. Quick Check:

   Launch browser then open page [OK]

Hint: Launch browser first, then create page with await [OK]

Common Mistakes:

• Calling newPage() before launching browser
• Missing await causing promise errors
• Mixing order of browser and page creation

3. Given this Playwright test snippet for a Svelte app:

await page.goto('http://localhost:3000');
await page.click('button#submit');
const text = await page.textContent('div#result');
console.log(text);

What will be logged if clicking the button updates the div#result to 'Success'?

medium

A. Error: selector not found

B. undefined

C. 'Success'

D. '' (empty string)

Solution

1. Step 1: Understand page.goto and click

   The test navigates to the page and clicks the button with id 'submit'.

2. Step 2: Check textContent after click

   Click updates div#result text to 'Success', so textContent returns 'Success'.

3. Final Answer:

   'Success' -> Option C

4. Quick Check:

   Click updates text, so textContent = 'Success' [OK]

Hint: Click updates text, textContent reads updated text [OK]

Common Mistakes:

• Assuming textContent returns undefined if element exists
• Not waiting for page navigation or updates
• Confusing selector syntax causing errors

4. Identify the error in this Playwright test code for a Svelte app:

await page.goto('http://localhost:3000');
await page.click('button.submit');
await expect(page.locator('div#result')).toHaveText('Success');

Why might this test fail even if the button click works?

medium

A. The selector 'button.submit' is incorrect if the button has id 'submit', not class 'submit'

B. The expect assertion syntax is invalid and will cause a syntax error

C. page.goto is missing await causing navigation failure

D. toHaveText cannot be used with page.locator

Solution

1. Step 1: Check selector correctness

   'button.submit' selects a button with class 'submit', but if button has id 'submit', selector should be 'button#submit'.

2. Step 2: Verify assertion and syntax

   expect with toHaveText on page.locator is valid syntax in Playwright.

3. Final Answer:

   The selector 'button.submit' is incorrect if the button has id 'submit', not class 'submit' -> Option A

4. Quick Check:

   Selector must match element attribute type [OK]

Hint: Match selector type: # for id, . for class [OK]

Common Mistakes:

• Using class selector when element has id
• Missing await on async calls
• Misunderstanding Playwright assertion syntax

5. You want to write a Playwright test for a Svelte app that fills a form with name and email, submits it, and checks for a success message. Which sequence of actions is correct?

hard

A. await expect(page.locator('div#message')).toHaveText('Form submitted!'); await page.fill('input#name', 'Alice'); await page.fill('input#email', '[e-mail]'); await page.click('button#submit');

B. await page.fill('input#name', 'Alice'); await page.fill('input#email', '[e-mail]'); await page.click('button#submit'); await expect(page.locator('div#message')).toHaveText('Form submitted!');

C. await page.fill('input#email', '[e-mail]'); await page.click('button#submit'); await page.fill('input#name', 'Alice'); await expect(page.locator('div#message')).toHaveText('Form submitted!');

D. await page.click('button#submit'); await page.fill('input#name', 'Alice'); await page.fill('input#email', '[e-mail]'); await expect(page.locator('div#message')).toHaveText('Form submitted!');

Solution

1. Step 1: Fill form fields before submitting

   Fill the name and email inputs first to provide data.

2. Step 2: Click submit and check success message

   After filling, click submit button, then assert the success message appears.

3. Final Answer:

   Fill inputs, click submit, then check message -> Option B

4. Quick Check:

   Fill before submit, then assert success [OK]

Hint: Fill inputs first, then submit, then check result [OK]

Common Mistakes:

• Clicking submit before filling inputs
• Checking success message before submit
• Filling inputs after submit