GitHub - mpeyper/react-hooks-testing-library: Simple component wrapper for testi...
source link: https://github.com/mpeyper/react-hooks-testing-library
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README.md
react-hooks-testing-library
Simple component wrapper and utilities for testing React hooks.
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
is build on top of the wonderful react-testing-library
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.
Using this library, you do not have to concern yourself with how the to interact construct, render or interact with the react component in order to test your hook. You can just use the hook directly and assert the resulting values.
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
// useTheme.js import { useState, createContext, useContext, useMemo } from 'react' const themes = { light: { primaryLight: '#FFFFFF', primaryDark: '#000000' }, dark: { primaryLight: '#000000', primaryDark: '#FFFFFF' } } const ThemesContext = createContext(themes) const useTheme = (initialTheme) => { const themes = useContext(ThemesContext) const [theme, setTheme] = useState(initialTheme) const toggleTheme = () => { setTheme(theme === 'light' ? 'dark' : 'light') } return useMemo(() => ({ ...themes[theme], toggleTheme }), [theme]) } // useTheme.test.js import { renderHook, cleanup, act } from 'react-hooks-testing-library' describe('custom hook tests', () => { afterEach(cleanup) test('should use theme', () => { const { result } = renderHook(() => useTheme('light')) const theme = result.current expect(theme.primaryLight).toBe('#FFFFFF') expect(theme.primaryDark).toBe('#000000') }) test('should update theme', () => { const { result } = renderHook(() => useTheme('light')) const { toggleTheme } = result.current act(() => toggleTheme()) const theme = result.current expect(theme.primaryLight).toBe('#000000') expect(theme.primaryDark).toBe('#FFFFFF') }) test('should use custom theme', () => { const customThemes = { light: { primaryLight: '#AABBCC', primaryDark: '#CCBBAA' }, dark: { primaryLight: '#CCBBAA', primaryDark: '#AABBCC' } } const wrapper = ({ children }) => ( <ThemesContext.Provider value={customThemes}>{children}</ThemesContext.Provider> ) const { result } = renderHook(() => useTheme('light'), { wrapper }) const theme = result.current expect(theme.primaryLight).toBe('#AABBCC') expect(theme.primaryDark).toBe('#CCBBAA') }) })
Installation
npm install --save-dev react-hooks-testing-library
API
renderHook(callback[, options])
Renders a test component that will call the provided callback
, including any hooks it calls, every time it renders.
Note:
testHook
has been renamed torenderHook
.testHook
will continue work in the current version with a deprecation warning, but will be removed in a future version.You should update any usages of
testHook
to userenderHook
instead.
Arguments
callback
(function()
) - function to call each render. This function should call one or more hooks for testing.options
(object
) - accepts the same options asreact-testing-library
'srender
function, as well as:initialProps
(object
) - the initial values to pass to thecallback
function
Returns
result
(object
)current
(any
) - the return value of thecallback
function
rerender
(function([newProps])
) - function to rerender the test component including any hooks called in thecallback
function. IfnewProps
are passed, the will replace theinitialProps
passed the thecallback
function for future renders.unmount
(function()
) - function to unmount the test component, commonly used to trigger cleanup effects foruseEffect
hooks.
cleanup()
Unmounts any React trees that were mounted with renderHook.
This is the same cleanup
function that is exported by react-testing-library
.
act(callback)
This is the same act
function that is exported by react-testing-library
.
Contributors
Thanks goes to these wonderful people (emoji key):
Michael Peyper
? ? ? ? ? ? ⚠️ ?
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
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