---
id: app/component-testing/react/examples
title: React examples
description: >-
Learn how to mount a React component, pass data to a React component, test
event handlers, and customize cy.mount() for React Router and Redux.
section: app
source_path: docs/app/component-testing/react/examples.mdx
version: 8d4bb7c9d1af182786c46b47bac667515b9e5d39
updated_at: '2026-08-07T13:17:53.464Z'
---
# React Examples
What you'll learn
* How to mount a React component
* How to pass data to a React component
* How to test event handlers
* How to customize `cy.mount()` for React Router and Redux
## Mounting Components
### Mounting a Component
The first step in testing a component is to mount it. This renders the component into a testbed and enable's the use of the Cypress API to select elements, interact with them, and run assertions.
To mount a React component, import the component into your spec and pass the component to the `cy.mount` command:
```
import { Stepper } from './stepper'it('mounts', () => { cy.mount() //Stepper should have initial count of 0 (default) cy.get('[data-cy=counter]').should('have.text', '0')})
```
### Passing Data to a Component
You can pass props to a component by setting them on the JSX passed into `cy.mount()`:
```
it('mounts', () => { cy.mount() //Stepper should have initial count of 100 cy.get('[data-cy=counter]').should('have.text', '100')})
```
### Testing Event Handlers
Pass a Cypress [spy](/llm/markdown/app/guides/stubs-spies-and-clocks.md#Spies) to an event prop and validate it was called:
```
it('clicking + fires a change event with the incremented value', () => { const onChangeSpy = cy.spy().as('onChangeSpy') cy.mount() cy.get('[data-cy=increment]').click() cy.get('@onChangeSpy').should('have.been.calledWith', 1)})
```
## Testing Error States
`cy.mount()` is an asynchronous Cypress command: it _enqueues_ the mount and returns immediately, before the component ever renders. When a component throws during render, the error surfaces as an uncaught exception rather than as a synchronous throw.
By default Cypress fails the test on any uncaught exception, so to assert on a render error you listen for it with [`cy.on('uncaught:exception')`](/llm/markdown/api/cypress-api/catalog-of-events.md#Uncaught-Exceptions) and return `false` to prevent Cypress from failing the test:
```
import { UserProfile } from './UserProfile'it('surfaces a render error', () => { cy.on('uncaught:exception', (err) => { // Assert on the error thrown during render... expect(err.message).to.include('user is required') // ...and return false so Cypress does not fail the test. return false }) cy.mount()})
```
### Testing Error Boundaries
The recommended way to handle render errors in React is an [Error Boundary](https://react.dev/reference/react/Component#catching-rendering-errors-with-an-error-boundary), which renders fallback UI via `getDerivedStateFromError()`. You can mount a component wrapped in your Error Boundary and assert that the fallback UI is displayed:
```
// ErrorBoundary.cy.jsximport { ErrorBoundary } from './ErrorBoundary'const errorMessage = 'I crashed!'const ChildWithError = () => { throw new Error(errorMessage)}it('displays the fallback UI on error', () => { // An Error Boundary renders fallback UI, but it does NOT stop the error // from propagating to Cypress as an uncaught exception. Cypress fails on // uncaught exceptions by default, so we must still suppress that behavior. cy.on('uncaught:exception', (err) => { // Only suppress the specific error we expect. expect(err.message).to.include(errorMessage) return false }) cy.mount( ) cy.get('header h1').should('contain', 'Something went wrong.')})
```
Where `ErrorBoundary` renders fallback UI from `getDerivedStateFromError()`:
```
// ErrorBoundary.jsximport React from 'react'export class ErrorBoundary extends React.Component { constructor(props) { super(props) this.state = { error: null } } static getDerivedStateFromError(error) { return { error } } render() { const { name } = this.props const { error } = this.state if (error) { return ( Something went wrong.
{`${name} failed to load`}
) } return this.props.children }}
```
## Custom Mount Commands
### Customizing `cy.mount()`
By default, `cy.mount()` is a simple passthrough to `mount()`, however, you can customize `cy.mount()` to fit your needs. For instance, if you are using providers or other global app-level setups in your React app, you can configure them here.
Below are a few examples that demonstrate using a custom mount command. These examples can be adjusted for most other providers that you will need to support.
### React Router
If you have a component that consumes a hook or component from [React Router](https://reactrouter.com/), make sure the component has access to a React Router provider. Below is a sample mount command that uses `MemoryRouter` to wrap the component.
* cypress/support/component.jsx
* cypress/support/component.tsx
```
import { mount } from 'cypress/react'import { MemoryRouter } from 'react-router-dom'Cypress.Commands.add('mount', (component, options = {}) => { const { routerProps = { initialEntries: ['/'] }, ...mountOptions } = options const wrapped = {component} return mount(wrapped, mountOptions)})
```
```
import { mount, MountOptions, MountReturn } from 'cypress/react'import { MemoryRouter, MemoryRouterProps } from 'react-router-dom'declare global { namespace Cypress { interface Chainable { /** * Mounts a React node * @param component React Node to mount * @param options Additional options to pass into mount */ mount( component: React.ReactNode, options?: MountOptions & { routerProps?: MemoryRouterProps } ): Cypress.Chainable } }}Cypress.Commands.add('mount', (component, options = {}) => { const { routerProps = { initialEntries: ['/'] }, ...mountOptions } = options const wrapped = {component} return mount(wrapped, mountOptions)})
```
To set up certain scenarios, pass in props that will get passed to `MemoryRouter` in the options. Below is an example test that ensures an active link has the correct class applied to it by initializing the router with `initialEntries` pointed to a particular route:
```
import { Navigation } from './Navigation'it('home link should be active when url is "/"', () => { // No need to pass in custom initialEntries as default url is '/' cy.mount() cy.get('a').contains('Home').should('have.class', 'active')})it('login link should be active when url is "/login"', () => { cy.mount(, { routerProps: { initialEntries: ['/login'], }, }) cy.get('a').contains('Login').should('have.class', 'active')})
```
### Redux
To use a component that consumes state or actions from a [Redux](https://react-redux.js.org/) store, create a `mount` command that will wrap your component in a Redux Provider:
* cypress/support/component.jsx
* cypress/support/component.tsx
```
import { mount } from 'cypress/react'import { Provider } from 'react-redux'import { getStore } from '../../src/store'Cypress.Commands.add('mount', (component, options = {}) => { // Use the default store if one is not provided const { reduxStore = getStore(), ...mountOptions } = options const wrapped = {component} return mount(wrapped, mountOptions)})
```
```
import { mount, MountOptions, MountReturn } from 'cypress/react'import { Provider } from 'react-redux'import { EnhancedStore } from '@reduxjs/toolkit'import { getStore } from '../../src/store'import { RootState } from './src/StoreState'declare global { namespace Cypress { interface Chainable { /** * Mounts a React node * @param component React Node to mount * @param options Additional options to pass into mount */ mount( component: React.ReactNode, options?: MountOptions & { reduxStore?: EnhancedStore } ): Cypress.Chainable } }}Cypress.Commands.add('mount', (component, options = {}) => { const { reduxStore = getStore(), ...mountOptions } = options const wrapped = {component} return mount(wrapped, mountOptions)})
```
The options param can have a store that is already initialized with data:
```
import { getStore } from '../redux/store'import { setUser } from '../redux/userSlice'import { UserProfile } from './UserProfile'it('User profile should display user name', () => { const user = { name: 'test person' } // getStore is a factory method that creates a new store const store = getStore() // setUser is an action exported from the user slice store.dispatch(setUser(user)) cy.mount(, { reduxStore: store }) cy.get('div.name').should('have.text', user.name)})
```
The `getStore` method is a factory method that initializes a new Redux store. It is important that the store be initialized with each new test to ensure changes to the store don't affect other tests.