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1 | 1 | # react-hooks-testing-library |
| 2 | + |
| 3 | +Simple component wrapper for testing React hooks. |
| 4 | + |
| 5 | +--- |
| 6 | + |
| 7 | +[](https://travis-ci.org/mpeyper/react-hooks-testing-library) |
| 8 | +[](https://www.npmjs.com/package/react-hooks-testing-library) |
| 9 | +[](http://www.npmtrends.com/react-hooks-testing-library) |
| 10 | +[](https://github.com/mpeyper/react-hooks-testing-library/blob/master/LICENSE.md) |
| 11 | + |
| 12 | +[](#contributors) |
| 13 | +[](http://makeapullrequest.com) |
| 14 | +[](https://github.com/mpeyper/react-hooks-testing-library/blob/master/CODE_OF_CONDUCT.md) |
| 15 | + |
| 16 | +[](https://github.com/mpeyper/react-hooks-testing-library/watchers) |
| 17 | +[](https://github.com/mpeyper/react-hooks-testing-library/stargazers) |
| 18 | +[](https://twitter.com/intent/tweet?text=Check%20out%20react-hooks-testing-library%20by%20%40mpeyper%20https%3A%2F%2Fgithub.com%2Fmpeyper%2Freact-hooks-testing-library%20%F0%9F%91%8D) |
| 19 | + |
| 20 | +## The problem |
| 21 | + |
| 22 | +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: |
| 23 | + |
| 24 | +> Invariant Violation: Hooks can only be called inside the body of a function component. |
| 25 | +
|
| 26 | +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. |
| 27 | + |
| 28 | +## The solution |
| 29 | + |
| 30 | +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 privings various useful utility functions for updating the inputs and retrieving the outputs of your amazing custom hook. |
| 31 | + |
| 32 | +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. |
| 33 | + |
| 34 | +### When to use this library |
| 35 | + |
| 36 | +1. You're writing a library with one or more custom hooks that are not directly tied a component |
| 37 | +2. You have a complex hook that is difficult to test through component interactions |
| 38 | + |
| 39 | +### When not to use this library |
| 40 | + |
| 41 | +1. Your hook is defined along side a component and is only used there |
| 42 | +2. Your hook is easy to test by just testing the components using it |
| 43 | + |
| 44 | +## Example |
| 45 | + |
| 46 | +```js |
| 47 | +// useTheme.js |
| 48 | +import { useState, createContext, useContext, useMemo } from 'react' |
| 49 | + |
| 50 | +const themes = { |
| 51 | + light: { primaryLight: '#FFFFFF', primaryDark: '#000000' }, |
| 52 | + dark: { primaryLight: '#000000', primaryDark: '#FFFFFF' } |
| 53 | +} |
| 54 | + |
| 55 | +const ThemesContext = createContext(themes) |
| 56 | + |
| 57 | +const useTheme = (initialTheme) => { |
| 58 | + const themes = useContext(ThemesContext) |
| 59 | + const [theme, setTheme] = useState(initialTheme) |
| 60 | + const changeTheme = () => { |
| 61 | + setTheme(theme === 'light' ? 'dark' : 'light') |
| 62 | + } |
| 63 | + return useMemo(() => ({ ...themes[theme], changeTheme }), [theme]) |
| 64 | +} |
| 65 | + |
| 66 | +// useTheme.test.js |
| 67 | +import { useHook, cleanup } from 'react-hooks-testing-library' |
| 68 | + |
| 69 | +describe('custom hook tests', () => { |
| 70 | + afterEach(cleanup) |
| 71 | + |
| 72 | + test('should use theme', () => { |
| 73 | + const { getCurrentValue } = useHook(() => useTheme('light')) |
| 74 | + |
| 75 | + const theme = getCurrentValue() |
| 76 | + |
| 77 | + expect(theme.primaryLight).toBe('#FFFFFF') |
| 78 | + expect(theme.primaryDark).toBe('#000000') |
| 79 | + }) |
| 80 | + |
| 81 | + test('should update theme', () => { |
| 82 | + const { getCurrentValue } = useHook(() => useTheme('light')) |
| 83 | + |
| 84 | + const { changeTheme } = getCurrentValue() |
| 85 | + |
| 86 | + changeTheme() |
| 87 | + |
| 88 | + const theme = getCurrentValue() |
| 89 | + |
| 90 | + expect(theme.primaryLight).toBe('#000000') |
| 91 | + expect(theme.primaryDark).toBe('#FFFFFF') |
| 92 | + }) |
| 93 | + |
| 94 | + test('should use custom theme', () => { |
| 95 | + const customThemes = { |
| 96 | + light: { primaryLight: '#AABBCC', primaryDark: '#CCBBAA' }, |
| 97 | + dark: { primaryLight: '#CCBBAA', primaryDark: '#AABBCC' } |
| 98 | + } |
| 99 | + |
| 100 | + const { getCurrentValue, addContextProvider } = useHook(() => useTheme('light')) |
| 101 | + |
| 102 | + addContextProvider(ThemesContext, { value: customThemes }) |
| 103 | + |
| 104 | + const theme = getCurrentValue() |
| 105 | + |
| 106 | + expect(theme.primaryLight).toBe('#AABBCC') |
| 107 | + expect(theme.primaryDark).toBe('#CCBBAA') |
| 108 | + }) |
| 109 | +}) |
| 110 | +``` |
| 111 | + |
| 112 | +## Installation |
| 113 | + |
| 114 | +```sh |
| 115 | +npm install react-hooks-testing-library |
| 116 | +``` |
| 117 | + |
| 118 | +## Usage |
| 119 | + |
| 120 | +```js |
| 121 | +// TODO: write this |
| 122 | +``` |
| 123 | + |
| 124 | +## Contributors |
| 125 | + |
| 126 | +Thanks goes to these wonderful people ([emoji key](https://github.com/kentcdodds/all-contributors#emoji-key)): |
| 127 | + |
| 128 | +<!-- ALL-CONTRIBUTORS-LIST:START - Do not remove or modify this section --> |
| 129 | +<!-- prettier-ignore --> |
| 130 | +| [<img src="https://avatars0.githubusercontent.com/u/23029903?v=4" width="100px;"/><br /><sub><b>Michael Peyper</b></sub>](https://github.com/mpeyper)<br />[💻](https://github.com/mpeyper/react-hooks-testing-library/commits?author=mpeyper "Code") [🎨](#design-mpeyper "Design") [📖](https://github.com/mpeyper/react-hooks-testing-library/commits?author=mpeyper "Documentation") [🤔](#ideas-mpeyper "Ideas, Planning, & Feedback") [🚇](#infra-mpeyper "Infrastructure (Hosting, Build-Tools, etc)") [📦](#platform-mpeyper "Packaging/porting to new platform") [⚠️](https://github.com/mpeyper/react-hooks-testing-library/commits?author=mpeyper "Tests") [🔧](#tool-mpeyper "Tools") | |
| 131 | +| :---: | |
| 132 | + |
| 133 | +<!-- ALL-CONTRIBUTORS-LIST:END --> |
| 134 | + |
| 135 | +This project follows the [all-contributors](https://github.com/kentcdodds/all-contributors) specification. Contributions of any kind welcome! |
| 136 | + |
| 137 | +## Issues |
| 138 | + |
| 139 | +_Looking to contribute? Look for the [Good First Issue](https://github.com/mpeyper/react-hooks-testing-library/issues?utf8=✓&q=is%3Aissue+is%3Aopen+sort%3Areactions-%2B1-desc+label%3A"good+first+issue"+) |
| 140 | +label._ |
| 141 | + |
| 142 | +### 🐛 Bugs |
| 143 | + |
| 144 | +Please file an issue for bugs, missing documentation, or unexpected behavior. |
| 145 | + |
| 146 | +[**See Bugs**](https://github.com/mpeyper/react-hooks-testing-library/issues?q=is%3Aissue+is%3Aopen+label%3Abug+sort%3Acreated-desc) |
| 147 | + |
| 148 | +### 💡 Feature Requests |
| 149 | + |
| 150 | +Please file an issue to suggest new features. Vote on feature requests by adding |
| 151 | +a 👍. This helps maintainers prioritize what to work on. |
| 152 | + |
| 153 | +[**See Feature Requests**](https://github.com/mpeyper/react-hooks-testing-library/issues?q=is%3Aissue+sort%3Areactions-%2B1-desc+label%3Aenhancement+is%3Aopen) |
| 154 | + |
| 155 | +### ❓ Questions |
| 156 | + |
| 157 | +For questions related to using the library, you can [raise issue here](https://github.com/mpeyper/react-hooks-testing-library/issues/new), or visit a support community: |
| 158 | + |
| 159 | +- [Reactiflux on Discord](https://www.reactiflux.com/) |
| 160 | +- [Stack Overflow](https://stackoverflow.com/questions/tagged/react-testing-library) |
| 161 | + |
| 162 | +## LICENSE |
| 163 | + |
| 164 | +MIT |
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