Why is there a need for another framework? the current approach is not producing fast sites, and this problem will not disappear by waiting for a faster CPU.

Foreword

Qwik in Action

Introduction to the frontend development. Now, the responsibility of creating good or bad applications depends on you because the means available are all there.

Introduction

Overview of TypeScript. TypeScript introduced types into an untyped language like Javascript to ensure code consistency.

TypeScript

Overview of the frontend architectures. In this lesson you will understand the difference from Client Side Rendering and Multi Page Application.

Frontend architectures

Overview of the hydration. In this lesson you will understand the difference from Hydration and Island architecture/Partial Hydration.

Hydration

React Server Component. In this lesson you will understand the difference from Server Component and Client Component.

React Server Component

Qwik resumability will change the frontend ecosystem, In this lesson you will understand why is so great.

Resumability, the Qwik way

Wrap up of frontend architectures module.

Summary Chapter 2

In this lesson you will be able to understand more about performance and you will understand how improve your application with less JavaScript.

Qwik, the framework built on top of closure-extraction

Resumability is the core concept behind Qwik. In this lesson you will understand better the process.

Resumability

Code Extraction is a topic hard to master, you will understand how it works with different approaches.

Code Extraction

JSX syntax is the most famous one because of React, but what about the other frameworks, Vue, Angular?

Why Qwik use JSX syntax

Summary Chapter 3

Let's see together the fundamentals of Qwik. In this lesson you will compare Webpack and Vite.

Getting started with Qwik

The Qwik build process is so important because the resumability process requires correct and intelligent bundling.

Qwik compilation Process

Qwik CLI and amazing tool to have a great Developer Experience with Qwik.

Technical requirements to start a new Qwik application

Qwik Middleware an easy and clever way to expose your RESTful APIs or GraphQL APIs.

Middleware

Wrap up of Getting Started with Qwik module.

Summary Chapter 4

In this lesson you will learn the pillars of SEO. You will lean few new terms and metrics that can help you to measure your application.

In this lesson you will learn the some new things about SEO and crawler.

Sitemap and robots files

Partytown an amazing library to execute third scripts in the service worker.

Partytown

Core Web Vitals are so important for own application. You will learn in detail all the metrics.

Core Web Vitals

Core Web Vitals Labs Data vs Field Data. These two information are so different, let's figure out the peculiarity of those.

Labs data vs Field data

Summary Chapter 5

SEO and Core Web Vitals

There are many ways to deploy a Qwik application. You can have your own server and deploy your Qwik application easily with the Qwik CLI and integrations.

Deploy Qwik in production

Cloud solution are a good alternative for a low cost pipeline and host. Nowadays these kind of services are so smart and great, you should try them.

Cloud solutions

With different team and many developers, it's important to master branching strategies to avoid problems during your day by day.

Branching strategies

Progressive Web App approach can be an alternative to the stores. You can publish you application with a lot of benefit with PWA.

Progressive Web App

Wrap up of Deploy Qwik in Production module.

Summary Chapter 6

Style an application is so important let's see how engage your Stakeholders into this process.

Style and render data with Qwik

CSS is so huge, there are a lot of ways to style your application with Qwik, let's see them together.

CSS and Built-In Styling Methods

Tailwind is an amazing library, let's see together how master it. I will share you some tips and tricks to use Tailwind in a better way.

Tailwind CSS

In this lesson you will learn how manage data with Qwik. There are a lot of APIs to explore, let's jump into the code.

Managing data with Qwik

Summary Chapter 7

In this lesson you will learn how architect a modern frontend end application.

Creating an e-commerce with Qwik and Supabase

In this lesson you will learn the trade offs of technical decisions. I share with you some tips and tricks.

Technological spike

In this lesson you will explore Supabase. This is an amazing service to leverage your business.

Supabase for your backend

A custom authentication is too complex and risky to implement from scratch. Let's use the Supabase auth to optimize our goals.

Let's talk about the Authentication process

Summary Chapter 8

Supabase CLI an handy tool to improve consistency across environments.

Supabase CLI

Let's use the Supabase CLI to manage our database migrations and schemas.

Supabase db migrations

In this lesson you will create the e-commerce homepage with the Supabase client to read the data.

Show products on our homepage

Every e-commerce has a detail page, let's create our product detail page with Qwik.

Product Detail

Cache is really useful and in this lesson I will explain in the detail how it works. I will share my experience in this topic with some cool analogies.

Cache-control headers

Summary Chapter 9

Rendering products with Orama full text search

Let's improve out application with a useful "Add to favorites" feature.

Add a product to your favorites list

In this lesson you will learn how to use Stripe to manage your payments in a secure way.

Adding cart and checkout process with Stripe

Let's try the Supabase database function. This is an easy way to allows us to do several things and also add some logic to our procedure.

Page views tracking

A real-time database with Supabase is so simple to implement, let's build together a new functionality with this great feature.

Real-time database

Summary Chapter 10

Let's explore together the benefit of testing. In this lesson you will explore the various types of tests, Unit Test, E2E, Visual regression tests and more.

Overview of application testing

Let's discuss together how and when testing is valuable for our business. 3X Explore/Expand/Extract can help us is this reasoning.

How much testing is enough? When do I write tests?

In this lesson you will lean the Test driven development TDD flow. It's a really good practice to put in place.

Test-Driven Development (TDD)

In this lesson you will lean how test your components with Cypress.

Let's add some tests with Cypress

Do you need a Qwik component library? Qwik UI is the project for you because can give you a lot of Qwik accessible components out of the box.

Qwik UI

Summary Chapter 11

Adding tests to our Qwik application

Let's explore a bit of history of Qwik. A new framework with a great past.

Final thoughts

Qwik and React together, no problem, qwikify$ is the API to solve your problems.

qwikify$

Qwik and Astro together, no problem, @qwikdev/astro is the library to solve your problems.

Qwik inside Astro application

Qwik and micro-frontends together, no problem, out of the box Qwik can manage this scenario with no external dependencies.

Micro-frontends with Qwik

Summary chapter 12

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( the primaryDescriptionMarkdown is long - several lines, include images, as long as you want )

In this course we <headline of what we do>. <why this technology is good> but <here's how learning it is problem>. 

In <the length of these lessons> we cover <three salient points about what we cover. Your BEST points>. Its <however long it is> and comes with <these bonus features, and reasons to buy. code, etc.>

It's taught by <author name> who <credibility, reason you should listen to them>. <social proof, if you have it yet>

<then you can list other supporting stuff you want to add, anything you want here>

-------
Example:
-------

We created a free course to create your first GraphQL server (from scratch) using Node and TypeScript. TypeScript and GraphQL are a powerful combo, but there's a lot of confusing edges if you're getting it setup the first time.

In this course we cover the basics of getting TypeScript setup with Node, how GraphQL works, and how to set up a GraphQL server using Apollo server. It's two hours long, it comes with complete code examples, and we walk through the code step-by-step.

It's taught by my friend, Shopify-engineer Hassan Djirdeh and he's integrated what he's learned using GraphQL in production as an engineer at Shopify. We've already had over 1,300 students enroll and it's been getting great reviews so far.

// ... and so on

Harness Qwik Resumable Architecture for Lightning-Fast Startup Times

In this course we <headline of what we do>. <why this technology is good> but <here's how learning it is problem>. 

( the summary is short - one or two lines )

Complete Guide to Qwik

How many times have we written a new piece of code and, due to a side effect, ended up breaking another feature we weren't expecting? These types of problems are commonly called regression errors. It often happens that if our code is strongly coupled and shares business logic, changing the logic connected to it also affects other parts of the application. How can we be sure that our changes or evolutions do not create problems in production?
A good test suite is able to prevent this kind of problems. Another benefit that should not be underestimated regarding testing is certainly that of being able to detect errors in advance directly during the development phase. So even before integrating the code into your final bundle, you may realize that something doesn't work as it should. This guarantees you save time and greatly reduces errors that can occur in production. In fact, if a problem arises a few weeks after our code has reached production, it will be more complex to identify and solve the problem.
Having a good test suite also allows us to facilitate refactoring activities, i.e., the process of fixing existing code to make it more manageable, and scalable but not only. Refactoring is an essential part of software development that allows us to evolve and improve the code of our application and reduce technical debt. Tests act as checkers that allow us to check whether the refactoring of our code has introduced errors or created regressions. Having clean code in the long term allows you to be more productive and therefore save money and time. The most important advantage, however, is the knowledge that we are following the implementation of high-quality code. Whether we are working on a small application, or even more so on a large one, we are aware that what we have tested works correctly, and therefore we have not changed the behavior which until now has allowed us to have an application that works correctly. To write a good test suite, however, it is important to dedicate effort and resources to be able to derive the benefits we have mentioned. Precisely because it takes time, many companies that I have had the opportunity to meet in my career have never fully believed in testing, a practice that was born many years ago and has evolved over time. With the advent of software, we have had an explosion of innovation and nowadays there are many programs to perform tests, both manual and automatic. Automatic ones were created precisely to limit the time investment that was mentioned before, and to speed up all those repetitive tasks that do not require a person to carry them out.
However, various types of tests touch on different areas of our application, because they are focused on different scopes. Let's look at this distinction together.

Unit tests are very important because they focus on the logic part of our application. They allow us to write robust and reliable code. This type of test focuses on a single functionality, and therefore we can only focus on a few lines of code. The functions that are tested are pure functions; i.e., they do not have side effects within them. The most classic example is testing the sum function, given a certain input (two numbers) I provide an output. Let's imagine inserting a logic within the function according to which, on Monday, the sum works differently compared to the other days of the week. In this case, we are adding unpredictability within our function and making our code very difficult to test. Pure functions give us a big advantage in terms of stability and predictability of our code because we can always have the situation under control.

We know with certainty that our business algorithms do not change. If we have discount policies that are based on the total amount of the goods our user is purchasing, we can verify the logic with a specific test and verify that, following the evolutions of our software, our algorithm is not affected.
This algorithm will be covered with various tests that verify the logic with different amounts and will be put under stress with edge cases that perhaps will bring out some cases not considered. A striking case could be that of having an amount which, net of promotions, entitles you to 20% of the total. Does this rule also apply if my user has already applied a 50% promotional discount for the spring sales? Which of the two discounts should I keep? If we think about it carefully, when we go to design an algorithm, these are questions that we already ask ourselves, but with the help of tests it is easier for us to define them. We have the possibility of isolating the scope leaving out the rest of the application to concentrate on the single piece of code. This approach therefore also helps us to better design our applications by focusing on real cases and avoiding predicting edge cases upfront. I know you are thinking that these are logical problems most of the time, and usually they are in the back-end. So, I'll give you another example, which is purely frontend. Let's take the product detail page seen before in our application. A unit test that can be developed is to verify that if I am inside the detail of a product, the name of the product I requested is present in the viewport. This guarantees us that our page is correct because by checking that all the information is in the right place, we can make the code that renders the detail page robust. The low cost in terms of effort and their simplicity make these types of tests an essential aid to our application development and the future evolutions we will make. This type of test also implicitly creates a sort of documentation of how the application should work and makes clear a whole series of cases that the application takes into consideration. By looking at a correctly written test suite we will be able to quickly understand the logic behind a certain piece of code, this aspect is very powerful. Another factor to consider is the fact of structuring our code with functions that are as atomic as possible to make any type of operation trivial. There should be no surprises in the code. This is a good practice not only for testing, but programming in general. If you have never read 

Clean Code: A Handbook of Agile Software Craftsmanship

 by Robert C. Martin, I recommend you do so because you will find many interesting ideas on best practices for writing quality code.

---
title: Overview of application testing
description: Let's explore together the benefit of testing. In this lesson you will explore the various types of tests, Unit Test, E2E, Visual regression tests and more.
---

# Overview of application testing

How many times have we written a new piece of code and, due to a side effect, ended up breaking another feature we weren't expecting? These types of problems are commonly called regression errors. It often happens that if our code is strongly coupled and shares business logic, changing the logic connected to it also affects other parts of the application. How can we be sure that our changes or evolutions do not create problems in production?
A good test suite is able to prevent this kind of problems. Another benefit that should not be underestimated regarding testing is certainly that of being able to detect errors in advance directly during the development phase. So even before integrating the code into your final bundle, you may realize that something doesn't work as it should. This guarantees you save time and greatly reduces errors that can occur in production. In fact, if a problem arises a few weeks after our code has reached production, it will be more complex to identify and solve the problem.
Having a good test suite also allows us to facilitate refactoring activities, i.e., the process of fixing existing code to make it more manageable, and scalable but not only. Refactoring is an essential part of software development that allows us to evolve and improve the code of our application and reduce technical debt. Tests act as checkers that allow us to check whether the refactoring of our code has introduced errors or created regressions. Having clean code in the long term allows you to be more productive and therefore save money and time. The most important advantage, however, is the knowledge that we are following the implementation of high-quality code. Whether we are working on a small application, or even more so on a large one, we are aware that what we have tested works correctly, and therefore we have not changed the behavior which until now has allowed us to have an application that works correctly. To write a good test suite, however, it is important to dedicate effort and resources to be able to derive the benefits we have mentioned. Precisely because it takes time, many companies that I have had the opportunity to meet in my career have never fully believed in testing, a practice that was born many years ago and has evolved over time. With the advent of software, we have had an explosion of innovation and nowadays there are many programs to perform tests, both manual and automatic. Automatic ones were created precisely to limit the time investment that was mentioned before, and to speed up all those repetitive tasks that do not require a person to carry them out.
However, various types of tests touch on different areas of our application, because they are focused on different scopes. Let's look at this distinction together.

## Unit tests

Unit tests are very important because they focus on the logic part of our application. They allow us to write robust and reliable code. This type of test focuses on a single functionality, and therefore we can only focus on a few lines of code. The functions that are tested are pure functions; i.e., they do not have side effects within them. The most classic example is testing the sum function, given a certain input (two numbers) I provide an output. Let's imagine inserting a logic within the function according to which, on Monday, the sum works differently compared to the other days of the week. In this case, we are adding unpredictability within our function and making our code very difficult to test. Pure functions give us a big advantage in terms of stability and predictability of our code because we can always have the situation under control.

We know with certainty that our business algorithms do not change. If we have discount policies that are based on the total amount of the goods our user is purchasing, we can verify the logic with a specific test and verify that, following the evolutions of our software, our algorithm is not affected.
This algorithm will be covered with various tests that verify the logic with different amounts and will be put under stress with edge cases that perhaps will bring out some cases not considered. A striking case could be that of having an amount which, net of promotions, entitles you to 20% of the total. Does this rule also apply if my user has already applied a 50% promotional discount for the spring sales? Which of the two discounts should I keep? If we think about it carefully, when we go to design an algorithm, these are questions that we already ask ourselves, but with the help of tests it is easier for us to define them. We have the possibility of isolating the scope leaving out the rest of the application to concentrate on the single piece of code. This approach therefore also helps us to better design our applications by focusing on real cases and avoiding predicting edge cases upfront. I know you are thinking that these are logical problems most of the time, and usually they are in the back-end. So, I'll give you another example, which is purely frontend. Let's take the product detail page seen before in our application. A unit test that can be developed is to verify that if I am inside the detail of a product, the name of the product I requested is present in the viewport. This guarantees us that our page is correct because by checking that all the information is in the right place, we can make the code that renders the detail page robust. The low cost in terms of effort and their simplicity make these types of tests an essential aid to our application development and the future evolutions we will make. This type of test also implicitly creates a sort of documentation of how the application should work and makes clear a whole series of cases that the application takes into consideration. By looking at a correctly written test suite we will be able to quickly understand the logic behind a certain piece of code, this aspect is very powerful. Another factor to consider is the fact of structuring our code with functions that are as atomic as possible to make any type of operation trivial. There should be no surprises in the code. This is a good practice not only for testing, but programming in general. If you have never read [Clean Code: A Handbook of Agile Software Craftsmanship](https://www.amazon.com/Clean-Code-Handbook-Software-Craftsmanship/dp/0132350882) by Robert C. Martin, I recommend you do so because you will find many interesting ideas on best practices for writing quality code.