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Full Coverage Testing

We are back to https://github.com/saucelabs-training/automation-best-practices and will work here for the rest of the workshop!

Everything will only be taught from my-react-app directory

🧠You will learn

✅How to write a component test

✅How to add a test id to our web app

✅How to correctly test a link and a tab

✅How to replace e2e tests with component tests

⚙️ Setup

We are back to https://github.com/saucelabs-training/automation-best-practices and will work here for the rest of the workshop!

  1. Stop all servers from previous session (Ctrl + C everything)
  2. cd my-react-app
  3. npm install
  4. npm start

Open application at http://localhost:3000/

🧪Testing Strategy

Expected Behavior Tested? Test Type Technologies
Application renders 🙅‍♂️ Component/UI/unit React testing library, Jest
Learn React link goes to correct location 🙅‍♂️
Learn React link opens in new tab 🙅‍♂️
App looks as expected on web and mobile 🙅‍♂️
Front-end performance is at least a B 🙅‍♂️
App is secure 🙅‍♂️
Multiple other testing types... 🙅‍♂️

What is the most basic test that we can write for our application?

  • How about making sure that our app renders?

🏋️‍♀️Write a cypress test to make sure that our app opens.

  • npx cypress open
  • Write a test to ensure our app renders cypress/integration/exercise.spec.js

❓Does this test guarantee that our app works as expected?

✅ App has corresponding class visible

✅ App renders in UI

❓ Does the app look as intended

❓ Does the app work as intended

🏋️‍♀️ Stop the application and rerun the test

✅ Confirms rendering works as expected

✅ Confirms server is running

What is the disadvantage of this test?

  1. Need a browser
  2. Need a server
  3. Need to deal with network issues
  4. Test will be slower
  5. Need an extra dependency (Cypress)
  6. Need to learn extra dependency API

Can we test the same thing more efficiently❓

Component tests

There are a few ways to test React components. Broadly, they divide into two categories:

  • Rendering component trees in a simplified test environment and asserting on their output.
  • Running a complete app in a realistic browser environment (also known as “end-to-end” tests)

ReactJS.org

What is a component test?

Component tests

Source: Yoni Goldberg

Advantages of component tests

❌ browser

❌ server

❌ network issues

✅ Tests run in ms

❌ extra dependency (Cypress)

❌ extra dependency API

Our app was created using create-react-app. With this method, we automatically get a few cool things for testing:

  • @testing-library
  • jest
  • And we get an automatic component test in src/App.test.js
//Exercise.test.js
test('renders learn react link', () => {
  render(<App />);
  const linkElement = screen.getByText(/learn react/i);
  expect(linkElement).toBeInTheDocument();
});

Testing Library is an opinionated framework that helps with component rendering and interactions.

Jest is a test runner and provides a bunch of capabilities like matchers and snapshot testing

Run the component test

Cypress doesn't support component tests yet. So we need to use other libraries.

  • Stop Cypress server
  • In your current directory (my-react-app), execute npm run test.
    • The tests should pass, even though our app isn't running.

💡 'p' to filter tests down to a specific file 💡 'o' to run tests only in the changed files

❓What does the Cypress test validate that the component test does not❓

💡How to add a test id to our app

Ever wondered how easy it is to add an attribute to an HTML element? Let's provide a better locator for our app.

🏋️‍♀️Add a data-testid attribute to our element

  1. Open my-react-app/src/App.js
  2. In the <a> of the App component add a data-testid property
        <a
          className="App-link"
          href="https://reactjs.org"
          target="_blank"
          rel="noopener noreferrer"
          data-testid="learn-link"
        >
  1. Open src/__tests__/Exercise.test.js
  2. Update the test to have this line of code instead const linkElement = screen.getByTestId('learn-link');
  3. Save and the test will automatically rerun

❓Is our app fully tested❓

Expected Behavior Tested? Test Type Technologies
Application renders ✅ Component React testing library, Jest
Learn React link goes to correct location 🙅‍♂️
Learn React link opens in new tab 🙅‍♂️
App looks as expected on web and mobile 🙅‍♂️
Front-end performance is at least a B 🙅‍♂️
App is secure 🙅‍♂️
Multiple other testing types... 🙅‍♂️

🔗Testing links (the right way)

Here's an e2e test to validate that a link works

it('should click link',()=>{
     cy.visit('/');
     cy.get('[data-testid=learn-link]').click().url().should('contain','ultimateqa.com');
 })

❓Why is this test bad❓

  1. Cypress will never have multi-tab support
  2. We should never need to test that a link is clickable, this is the browser's native behavior
  3. We should never need to test that a link opens a new tab

🏋️‍♀️Write a test to validate link behavior

💡We don't need a browser to actually test a link click, so why not use a fast component test?

  1. Make sure that you run npm test if it's not running already
  2. Go to src/__tests__/Exercise.test.js and write a test that looks like this
test('link has correct url', () => {
  //render our App component in a virtual DOM
  render(<App />);
  const linkElement = screen.getByTestId('learn-link')
  expect(linkElement.href).toContain('ultimateqa');
})
  1. Save and the test runs automatically

❓What does this check actually test❓

❓What if we wanted to test that the link opens in a new tab❓

👀 Working with 'target' attribute

🏋️‍♀️Write a component test to validate that link opens in a new tab

❓Is our app fully tested now❓

Expected Behavior Tested? Test Type Technologies
Application renders ✅ Component React testing library, Jest
Learn React link goes to correct location ✅ Component React testing library, Jest
Learn React link opens in new tab ✅ Component React testing library, Jest
App looks as expected on web and mobile 🙅‍♂️
Front-end performance is at least a B 🙅‍♂️
App is secure 🙅‍♂️

📝Summary

✅An e2e test (Cypress) tests the connection from the front-end to the back-en

✅Most of the functionality of a modern web app (React, Vue, Angular) can be tested with component tests in a virtual DOM. We did this by testing links, tabs, and correct HTML

Let's go implement visual testing