Book Image

Svelte with Test-Driven Development

By : Daniel Irvine
Book Image

Svelte with Test-Driven Development

By: Daniel Irvine

Overview of this book

Svelte is a popular front-end framework used for its focus on performance and user-friendliness, and test-driven development (TDD) is a powerful approach that helps in creating automated tests before writing code. By combining them, you can create efficient, maintainable code for modern applications. Svelte with Test-Driven Development will help you learn effective automated testing practices to build and maintain Svelte applications. In the first part of the book, you’ll find a guided walkthrough on building a SvelteKit application using the TDD workflow. You’ll uncover the main concepts for writing effective unit test cases and practical advice for developing solid, maintainable test suites that can speed up application development while remaining effective as the application evolves. In the next part of the book, you’ll focus on refactoring and advanced test techniques, such as using component mocks and writing BDD-style tests with the Cucumber.js framework. In the final part of the book, you’ll explore how to test complex application and framework features, including authentication, Svelte stores, and service workers. By the end of this book, you’ll be well-equipped to build test-driven Svelte applications by employing theoretical and practical knowledge.
Table of Contents (22 chapters)
1
Part 1: Learning the TDD Cycle
8
Part 2: Refactoring Tests and Application Code
16
Part 3: Testing SvelteKit Features

Adding a Playwright test for offline access

Service workers tend to have a specific intent. In our case, the service worker enables the application to be used offline: loading the application causes it to be cached. If the network is no longer accessible, the next page load will be served from this cache, courtesy of the service worker.

Therefore, the Playwright test needs to test the application’s behavior when there’s no network connection.

At the time of writing, Playwright’s support for service worker events is experimental, so it needs to be enabled using the PW_EXPERIMENTAL_SERVICE_WORKER_NETWORK_EVENTS flag in your package.json file:

{
  "scripts": {
    ...,
  "test": "PW_EXPERIMENTAL_SERVICE_WORKER_NETWORK_EVENTS=1
    playwright test",
  ...
  }
}

Once that’s done, we’re ready to write our tests. We need two helper functions...