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

Setting up a Playwright world object

How does Cucumber execute your test? Just like with the Playwright tests, we need a running application server and a running browser to drive the user interface (UI). In this section, we’ll write all the code that gets the environment ready for test execution.

Cucumber.js uses the concept of a world object that describes the contextual information that is shared between each scenario step. This is an object that is bound to the this variable in each step. We also get access to it in special Before and After hooks, which are run before and after each scenario.

The world object should contain functions (and state) that allow you to drive the UI. Since you’ve already learned and used the Playwright API for locating objects on a page, it would be marvelous if we could use that same API. It turns out we can indeed do this. We can also use the same expect API we’re used to as well, and we’ll do that in the next section...