Despite the fact that Cypress is an application that runs natively on your machine, you can install it and add it as a dependency just like all other dependencies in your package.json file. So let's install Cypress and get our project ready to start end-to-end testing with Cypress.

Install, Configure, and Script Cypress for JavaScript Web Applications

Install and Run Cypress

Instructor: 00:02 To install Cypress into our project, we're going to run `npm install` and save it as a devDependency cypress.

#### Terminal
```bash
npm install --save-dev cypress
```

With that installed, we can run `npx cypress --help`, and we'll see here all the commands that are available to us.

```bash
npx cypress --help
```

00:15 We want to run the `open` command to see the Cypress app. Let's run `npx cypress open`, and that will pull up the Cypress app which was installed onto your computer.

![cypress app opened with npx cypress open](https://res.cloudinary.com/dg3gyk0gu/image/upload/v1574727281/transcript-images/jest-install-and-run-cypress-cypress-app-first-opened.png)

Here we have a bunch of examples that have been added automatically for us, and so we can quickrun all the specs.

00:32 That's going to pop open Chrome automatically for us, and it's going to run all through all of those tests for us automatically. As fun as it is to watch it run through the Kitchen Sink of examples, we're going to go ahead and stop this here. We'll go back to our tests, we'll stop that. We can just quit this, come back to our code editor.

00:51 Let's take a look at the files that were added to our project. First, we had a `cypress.json` added. It's just an empty object for now, and then we also have this `cypress` directory. This is where all of our Cypress testing related files go. We have support plugins integration and fixtures.

01:06 Fixtures are a bunch of JSON files. Integration is where we have all of our test. We've got a bunch of stuff as examples that Cypress has preloaded for us, so we can learn from those examples.

01:17 You'll notice that we've got a bunch of red stuff going on in here. That's because our ESLint does not configure to support Cypress, so let's go ahead and make that happen. I'm going to `npm install` as a dev dependency, `eslint-plugin-cypress`. That's going to add a couple ESList rules that will be useful for us.

```bash
npm install --save-dev eslint-plugin-cypress
```

01:35 Then right in the Cypress directory, we're going to add a `.eslintrc.js` file. Then in this file, we'll do a `module.exports` which will equal that plugin we just installed, ESLint plugin Cypress. That'll add a couple rules for us. We'll say `env` is Cypress globals `true`.

#### cypress/.eslintrc.js
```js
Learn more or give us feedback
module.exports = {
  plugins: ['eslint-plugin-cypress'],
  env: {'cypress/globals': true},
}
```

01:54 The globals are coming from the ESLint plugin that we installed. That will support the describe in the global variables that we're using. Then we'll also add an `extends` so that we can extend the plugin `cypress/recommended` rule set. Just for good measure, I'll also extend the `kentcdodds` import for a couple other rules that I like here.

```js
Learn more or give us feedback
module.exports = {
  plugins: ['eslint-plugin-cypress'],
  extends: ['kentcdodds', 'kentcdodds/import', 'plugin:cypress/recommended'],
  env: {'cypress/globals': true},
}
```

02:17 The reason that I'm doing that is even though ESLint is automatically going to merge this configuration with the root level configuration, there are a couple of conflicts between the Cypress plugin and the Jest plugin and I don't want to have those conflicts. What I'm going to do here is I'll say `root: true`.

```js
Learn more or give us feedback
module.exports = {
  root: true,
  plugins: ['eslint-plugin-cypress'],
  extends: ['kentcdodds', 'kentcdodds/import', 'plugin:cypress/recommended'],
  env: {'cypress/globals': true},
}
```

02:32 That way, ESLint will stop here as it's looking at the file system for the configuration to use for a particular file. Another thing that Cypress adds that I want to take care of is Cypress adds a video and screenshots directory. I don't want to commit those to source control. In .gitignore, we'll say `cypress/videos`, and `Cypress/screenshots`, and that gets me working.

#### .gitignore
```
dist
node_modules
coverage
cypress/videos
cypress/screenshots
```

02:53 In review, what we did here was we installed Cypress into our dev dependencies of our package JSON. We ran Cypress open, and that automatically created a Cypress JSON configuration file for us and a bunch of files in the Cypress directory.

03:07 Then, we configured ESLint to support Cypress. We configured git to ignore the videos and screenshots directory that Cypress is going to create for us. That's how we get Cypress installed into our project.


 is an incredibly powerful web testing tool. It’s capable of testing any web application. Its architecture places it a cut above similar end-to-end testing tools. Its developer experience is best-in-class. And because Cypress runs your tests in the same context as the rest of your application, you’re able to get speed, reliability, and debuggability that are just a long - distant dream with similar tools. The catch? There is no catch. Cypress is exceptional.

In this course, we’ll go over how you can install, configure, and script Cypress to test modern, real - world JavaScript web applications.

What's changed in Install, Configure, and Script Cypress for JavaScript Web Applications

Intro to Install, Configure, and Script Cypress for JavaScript Web Applications 

Cypress starts out your project with a ton of tests, let’s remove those and add our first test that verifies our calculator can add two numbers together using the Cypress selector playground and Cypress commands.

Write the First Cypress Test

Cypress is fairly simple to configure, but it’s important to optimize our experience in testing Cypress. We’ll configure the baseUrl to make it easier to visit our app and we’ll also move our test files to a folder called e2e to make it more clear what types of tests we want to write with Cypress. We’ll use the cypress.json file, but Cypress can also be configured via command line flags and environment variables.

Configure Cypress in cypress.json

Our selectors are pretty ridiculous, mostly because we’re using CSS-in-JS and css modules for our react application. But even if we weren’t, using class names as selectors for our application testing is pretty brittle and not really testing in the way a user would. So instead let’s use cypress-testing-library to improve our selectors and make it easier to read our tests.

There's been a small breaking change to Cypress Testing Library that affects the code in this video. [Learn more here.](https://github.com/testing-library/cypress-testing-library/releases/tag/v6.0.0)

Installing Cypress Testing Library

We want to make starting cypress as simple as possible for local development and we need to be able to run a single script that exits when the tests are complete for continuous integration. So let’s add a few scripts to get ourselves setup for this development experience.

Script Cypress for Local Development and Continuous Integration

One of the greatest features of Cypress is how awesome the experience of debugging tests is. You do have to get used to the asynchronous nature of E2E testing, but once you get the hang of that debugging is pretty straightforward, and the ability to debug your own source code is awesome. The fact that your test and source code are executed in the same context also gives you some powerful advantages as well. You can potentially even expose some internal state to your Cypress app.

Debug a Test with Cypress

Let’s write a test to fill out our registration form. Because we’ll be running this against a live backend, we need to generate the user’s information to avoid re-runs from trying to create new users that already exist. There are trade-offs with this approach. You should probably also clean out the application database before all of your tests start (how you accomplish this is pretty application-specific). Also, if your application requires email confirmation, I recommend you mock that on the backend and automatically set the user as confirmed during tests.

There's been a small breaking change to Cypress Testing Library that affects the code in this video. [Learn more here.](https://github.com/testing-library/cypress-testing-library/releases/tag/v6.0.0)

 Test User Registration with Cypress

Because Cypress allows you to use all the developer tools you’re used to from Google Chrome, you can actually use Cypress as your main application development workflow. If you’ve ever tried to develop a feature that required you to be in a certain state you’ve probably felt the pain of repeatedly refreshing the page and clicking around to get into that state. Instead, you can use cypress to do that and developer your application entirely in Cypress.

There's been a small breaking change to Cypress Testing Library that affects the code in this video. [Learn more here.](https://github.com/testing-library/cypress-testing-library/releases/tag/v6.0.0)

Cypress Driven Development

Normally I prefer to test error states using integration or unit tests, but there are some situations where it can be really useful to mock out a response to test a specific scenario in an E2E test. Let’s use the cypress server and route commands to mock a response from our registration request to test the error state.

Simulate HTTP Errors in Cypress Tests

To test user login we need to have a user to login with. We could seed the database with a user and that may be the right choice for your application. In our case though we’ll just go through the registration process again and then login as the user and make the same assertions we made for registration.

There's been a small breaking change to Cypress Testing Library that affects the code in this video. [Learn more here.](https://github.com/testing-library/cypress-testing-library/releases/tag/v6.0.0)

Test User Login with Cypress

We’re duplicating a lot of logic between our registration and login tests and not getting any additional confidence, so lets reduce the duplicate logic and time in our tests using cy.request to get a user registered rather than clicking through the application to register a new user.

There's been a small breaking change to Cypress Testing Library that affects the code in this video. [Learn more here.](https://github.com/testing-library/cypress-testing-library/releases/tag/v6.0.0)

Create a User with cy.request from Cypress

We’re going to need a newly created user for several tests so let’s move our cy.request command to register a new user into a custom Cypress command so we can use that wherever we need a new user.

There's been a small breaking change to Cypress Testing Library that affects the code in this video. [Learn more here.](https://github.com/testing-library/cypress-testing-library/releases/tag/v6.0.0)

Keep Tests Isolated and Focused with Custom Cypress Commands

Use Custom Cypress Command for Reusable Assertions

For most applications you’re going to need to be logged in as a user to interact with the application. Let’s see how we can register as a new user and login as that user to test using the application as a logged in user.

There's been a small breaking change to Cypress Testing Library that affects the code in this video. [Learn more here.](https://github.com/testing-library/cypress-testing-library/releases/tag/v6.0.0)

Run Tests as an Authenticated User with Cypress

We’re duplicating a bunch of commands between our new test and the login test and it’s not giving us any more confidence that the application is working properly. So let’s do the same thing we did with registration and make a cy.request command to login with the newly created user to speed up our test and make it more focused.

There's been a small breaking change to Cypress Testing Library that affects the code in this video. [Learn more here.](https://github.com/testing-library/cypress-testing-library/releases/tag/v6.0.0)

Use cy.request from Cypress to Authenticate as a New User

It’s pretty likely that we’ll need to login as a particular user for many tests, let’s take our cy.request command and turn it into a custom command to make it easier for the places we’ll be needing a logged in user.

There's been a small breaking change to Cypress Testing Library that affects the code in this video. [Learn more here.](https://github.com/testing-library/cypress-testing-library/releases/tag/v6.0.0)

Use a Custom Cypress Command to Login as a User

Combine Custom Cypress Commands into a Single Custom Command

Because Cypress runs in a real Chrome browser, we can install extensions, like React DevTools. The tricky bit will be to make our application hook up to the extension properly.

Install and Run Cypress

Transcript

Install and Run Cypress