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

Test-driving the page component

It’s time to create the page component that exists for the route. As ever, we’ll start with a test:

  1. Create the src/routes/birthdays/page.test.js file and add the following imports. The last of these is for the page component itself. Because SvelteKit expects the component for a route to exist in a file named +page.svelte, we may as well give the component the name Page (that is what it is, after all):
    import { describe, it, expect } from 'vitest';
    import {
      render,
      screen
    } from '@testing-library/svelte';
    import Page from './+page.svelte';
  2. Next, let’s write out the test. The key part here is that Page gets passed a data prop, which needs to match the structure of our load function. In the actual runtime environment, SvelteKit will invoke the load function and then render the component in +page.svelte with the data prop set to the result of the load function:
    describe...