Testing Library is a great bunch of utils to write tests for your UI. It has become the favorite testing choice of many users since it encourages you to write more maintainable and reliable tests, encourages best practices, and doesn't focus on implementation but behavior.

However, testing your app correctly with Testing Library is not always straightforward. _What query variant fits better for this situation? How should I check appearance/disappearance? What is the best way to handle async behaviors? Why am I seeing this particular error or warning? Why am I not getting the expected element?_ These are very typical questions while writing tests with Testing Library.

You are not alone! This course aims to help you master these situations with the assistance of `eslint-plugin-testing-library`: the official ESLint plugin for Testing Library.

The course will boost your Testing Library skills by using this plugin
as a companion when writing tests. You will get instant feedback by linting your tests code, so you can **follow best practices and anticipate common mistakes for Testing Library**, as well as better understand its utils and their main purposes.

Get ready to say goodbye to flaky tests!

Master writing Testing Library tests with eslint-plugin-testing-library by anticipating common mistakes and following best practices

Master Testing Library with ESLint Plugin

---
title: Working with the provided sample codes
description: In this course we won't be building an app from scratch, but fixing existing examples and apps containing errors. We need to download and setup the provided sample codes to be able to work with them in the corresponding lessons.
isPublicLesson: true
privateVideoUrl: https://fullstack.wistia.com/medias/mfiaxx2gqn
---

# Working with the provided sample codes

In most of the courses, you will start an app from scratch and iterate through it across the entire course. That's not the case for this course!

Since we want to visit many common errors and mistakes when writing tests, we are providing several demo apps for many lessons that already contain tests with specific issues for the lessons.

## Downloading all sample codes

:::note
🧑‍💻 Download the complete set of demo projects and exercises for this course [here! 🔗](https://d2uusema5elisf.cloudfront.net/courses/master-writing-testing-library-tests-using-eslint-plugin-testing-library/module_02/lesson_02.03/public/master-testing-library-with-eslint-plugin_all-demo-apps.zip)
:::

Here we are going to see how to download those demo apps and set them up in our machine:

1.  Download the entire set of demo projects for the course from the link attached at the top of this section.
2.  (Optional) Move the zip downloaded to a different folder, since we are going to use its content across the entire course.
3.  Extract the `master-testing-library-with-eslint-plugin_all-demo-apps.zip` you just downloaded.
4.  Open the folder extracted with the same name: `master-testing-library-with-eslint-plugin_all-demo-apps`
5.  (Optional) Feel free to rename the folder to something you are more confortable with!

All demo apps downloaded and extracted! You won't need to do these steps again, unless you delete the downloaded folder.

## Navigating into a demo app for a specific lesson

Inside the folder extracted in the previous section you'll see a bunch of other zips named like `01.02_working-with-sample-codes`. The numbers indicate the module and lesson they belong to (e.g. `01.02` means module 1 - lesson 2), and the name after the underscore is the title of the corresponding lesson, just for convenience.

For working in one of such demo apps, please follow these instructions:

1.  Open the `master-testing-library-with-eslint-plugin_all-demo-apps` folder
2.  Extract the desired lesson. For example, if you are about to start the module 2 - lesson 7, you need to extract the file named `02.07_no-render-in-setup.zip`.
3.  Open a terminal and navigate to the folder where you extracted the `master-testing-library-with-eslint-plugin_all-demo-apps` directory, then navigate to the lesson directory you just extracted. For the module 2 - lesson 7 example, it would be

In this course we won't be building an app from scratch, but fixing existing examples and apps containing errors. We need to download and setup the provided sample codes to be able to work with them in the corresponding lessons.