Testing React Components

Question 1

What is JEST?

Answer 1

Is a test runner and test assertion library.

Question 2

What is the first principle of unit tests?

Answer 2

Never trust a test until you have seen it fail.

Question 3

When to write tests?

Answer 3

When the value of the tests outweigh the test execution time and the complexity it adds up to the code base.

Question 4

What aspects of the application should my react unit tests cover?

Answer 4

The user interface.

Question 5

What does the storybook library do?

Answer 5

Render the *.story.js files in a ‘listable’ and ‘searchable’ manner

Question 6

What is the ‘React Testing Library’ guideline?

Answer 6

The more your tests resembles the way your software is used the more confidence you’ll get.

Question 7

How would you test a label element that shows “Username:” following the React Testing Library guidelines and best practices? Why not looking for a label element containing a specific id or other very-specific css selector?

Answer 7

getByText(‘username’). Because it will make it hard to refactor/change that component since we’re testing the implementation and not the final result (which is ‘username:’ being render).