The problem
You're writing an awesome custom hook and you want to test it, but as soon as you call it you see
the following error:
Invariant Violation: Hooks can only be called inside the body of a function component.
You don't really want to write a component solely for testing this hook and have to work out how you
were going to trigger all the various ways the hook can be updated, especially given the
complexities of how you've wired the whole thing together.
The solution
The react-hooks-testing-library allows you to create a simple test harness for React hooks that
handles running them within the body of a function component, as well as providing various useful
utility functions for updating the inputs and retrieving the outputs of your amazing custom hook.
This library aims to provide a testing experience as close as possible to natively using your hook
from within a real component.
Using this library, you do not have to concern yourself with how to construct, render or interact
with the react component in order to test your hook. You can just use the hook directly and assert
the results.
When to use this library
- You're writing a library with one or more custom hooks that are not directly tied a component
- You have a complex hook that is difficult to test through component interactions
When not to use this library
- Your hook is defined along side a component and is only used there
- Your hook is easy to test by just testing the components using it
Example
useCounter.js
import { useState, useCallback } from 'react'
function useCounter() {
const [count, setCount] = useState(0)
const increment = useCallback(() => setCount((x) => x + 1), [])
return { count, increment }
}
export default useCounter
useCounter.test.js
import { renderHook, act } from '@testing-library/react-hooks'
import useCounter from './useCounter'
test('should increment counter', () => {
const { result } = renderHook(() => useCounter())
act(() => {
result.current.increment()
})
expect(result.current.count).toBe(1)
})
More advanced usage can be found in the
documentation.
Installation
npm install --save-dev @testing-library/react-hooks
Peer Dependencies
react-hooks-testing-library does not come bundled with a version of
react or
react-test-renderer to allow you to install
the specific version you want to test against. Generally, the installed versions for react and
react-test-renderer should have matching versions:
npm install react@^16.9.0
npm install --save-dev react-test-renderer@^16.9.0
NOTE: The minimum supported version of
reactandreact-test-rendereris^16.9.0.
API
See the API reference.
Contributors
Thanks goes to these wonderful people (emoji key):
This project follows the all-contributors specification.
Contributions of any kind welcome!
Issues
Looking to contribute? Look for the
Good First Issue
label.
? Bugs
Please file an issue for bugs, missing documentation, or unexpected behavior.
? Feature Requests
Please file an issue to suggest new features. Vote on feature requests by adding a ?. This helps
maintainers prioritize what to work on.
❓ Questions
For questions related to using the library, you can
raise issue here, or
visit a support community:
LICENSE
MIT