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

Replacing Behavior with a Side-By-Side Implementation

In the previous two chapters you built out a fully formed repository and an API for accessing it. Now it’s time to complete the story arc by updating both the SvelteKit loader and form actions to use the API instead of the repository.

It’s worth pointing out that this isn’t a necessary step: it would be perfectly acceptable to keep the SvelteKit server pieces pointing directly at the repository.

But reworking our existing code to point at the new API endpoints will introduce you to two ideas: first, that of a side-by-side implementation, which is a way to use tests to replace the existing code while ensuring the test suite remains on Green. The second is the use of a test double to shield the unit tests from SvelteKit. The test double takes the place of the framework code, avoiding a real network call out to the API – which wouldn’t work anyway since the API isn’t running within our...