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

Avoiding component mocks

This section covers how to build your application without using component mocks. Of course, the application we’ve built up to this point hasn’t used any, so you already know it’s possible.

The SvelteKit application we’ve built has a page route component that renders a list of Birthday components and a BirthdayForm component. Both of these components are covered by their own test suites, so they are certainly candidates for using component mocks. The page route component would simply check that it renders Birthday and BirthdayForm in the right way, and avoid testing any of the birthdays themselves.

But there’s not much point in doing this. Neither of these components has any behavior on mount, so there’s no trouble in letting them render.

The biggest risk you have in not using component mocks is that of overtesting. This is when you repeat the tests of a child component in the tests for the parent component...