Gain insights into testing React apps effectively. Learn about unit tests with Jest and automated integration tests using Selenium to ensure robust, customer-ready software.

Complete Guide to Testing React Apps with Jest and Selenium.jpg

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This course will teach you to properly test your React applications, starting from basic unit tests with Jest to automated integration tests using Selenium. You will learn everything from the ground up to the most advanced concepts that will give you confidence in shipping your software to customers.

Complete Guide to Testing React Apps with Jest and Selenium

## Defining tests
__Grouping tests:__ `describe('<Component />', () => {});`.

__Individual tests:__ `it('does something', () => {});` or `test('does something', () => {});`.

## Setup and teardown
`beforeEach(() => {})`: Runs before each test.

`afterEach(() => {})`: Runs after all tests.

`beforeAll(() => {})`: Runs once before all tests.

`afterAll(() => {})`: Runs once after all tests.

## Assertions
`expect(value)` is always the first step to assert something. It contains the following functions:
- `expect(value).toBe(value)`: Shallow equality check
- `expect(value).toEqual(value)`: Deep equality check
- `expect(value).toBeTruthy()` and `expect(value).toBeFalsy()`
- `expect(value).toBeDefined()`
- `expect(value).toBeNull()`
- `expect(value).toBeGreaterThan(value)`, `expect(value).toBeGreaterThanOrEqual(value)`, `expect(value).toBeLessThan(value)`, and `expect(value).toBeLessThanOrEqual(value)`
- `expect(value).toBeCloseTo(value, numDigits)`
- `expect(value).toMatch(regex)`: Check a string against a regex.
- `expect(value).toContain(value)`: Check a data structure for containing a value.
- `expect(value).toBeInstanceOf(type)`: Instance check

You can also add `.not` to expect to flip the assertion around:
`expect(value).not.toEqual('abacaba')` and `expect(value).not.toBeInstanceOf(Abacaba)`

__Mocking__
- Create a mock function: `jest.fn()`.
- Check if a mock function was called: `expect(mock).toHaveBeenCalled()` and `expect(mock).toHaveBeenCalledWith(args)`

# Defining tests
__Grouping tests:__ `describe('<Component />', () => {});`.

__Individual tests:__ `it('does something', () => {});` or `test('does something', () => {});`.

# Setup and teardown
`beforeEach(() => {})`: Runs before each test.

`afterEach(() => {})`: Runs after all tests.

`beforeAll(() => {})`: Runs once before all tests.

`afterAll(() => {})`: Runs once after all tests.

# Assertions
`expect(value)` is always the first step to assert something. It contains the following functions:
- `expect(value).toBe(value)`: Shallow equality check
- `expect(value).toEqual(value)`: Deep equality check
- `expect(value).toBeTruthy()` and `expect(value).toBeFalsy()`
- `expect(value).toBeDefined()`
- `expect(value).toBeNull()`
- `expect(value).toBeGreaterThan(value)`, `expect(value).toBeGreaterThanOrEqual(value)`, `expect(value).toBeLessThan(value)`, and `expect(value).toBeLessThanOrEqual(value)`
- `expect(value).toBeCloseTo(value, numDigits)`
- `expect(value).toMatch(regex)`: Check a string against a regex.
- `expect(value).toContain(value)`: Check a data structure for containing a value.
- `expect(value).toBeInstanceOf(type)`: Instance check

You can also add `.not` to expect to flip the assertion around:
`expect(value).not.toEqual('abacaba')` and `expect(value).not.toBeInstanceOf(Abacaba)`

__Mocking__
- Create a mock function: `jest.fn()`.
- Check if a mock function was called: `expect(mock).toHaveBeenCalled()` and `expect(mock).toHaveBeenCalledWith(args)`

A list of some common Jest functions and matches that you may find helpful.

Introduction

Introductory Quiz

Write Your First Tests

Basic Testing Exercises

More Tests

Mocking Modules in Unit Tests

Mocking Exercises

More on Integration Tests

Bonus: Custom Matchers

Jest Cheatsheet

Defining tests

Setup and teardown