Automatically generate prop fixtures and snapshot tests for your React components
```js
import snap from 'jest-auto-snapshots';
import MyComponent from '../MyComponent';
snap(MyComponent, '../MyComponent.jsx');
```
↓
```
PASS examples/MyComponent/__tests__/MyComponent.test.js
jest-auto-snapshots > MyComponent
✓ Matches snapshot when passed only required props (3ms)
✓ Matches snapshot when passed all props (2ms)
✓ Matches snapshot when boolean prop "booleanProp" is set to: "false" (1ms)
```
## Why?
> [Snapshot tests](https://facebook.github.io/jest/docs/en/snapshot-testing.html) are a very useful tool whenever you want to make sure your UI does not change unexpectedly.
`jest` and `react-test-renderer` are fantastic tools, but writing tests for all the different possible rendering states and maintaining props is tedious. Really, we just want to know when & where a component snapshot changes and if that change was intentional.
For example, take the following simple component: ``. In order to make sure `MyComponent` is fully covered in snapshot tests, we would have to write (and maintain) _two_ separate tests for the boolean `active` state.
`jest-auto-snapshots` can detect the different prop types your component uses and _create_ those shapshot tests for you!
If `MyComponent`'s props ever get changed/added/removed `jest-auto-snapshots` will just create and run new snapshot tests.
See the bigger [example below](https://github.com/icd2k3/jest-auto-snapshots#example) for more info.
#### What this does (or aspires to do):
- Save you time when writing simple A -> B rendering tests.
- Automatically update, add, and remove snapshot tests when your component props change.
- Ensure that all possible component rendering states are covered.
#### What it doesn't do:
- _Deeply_ test all prop possibilities nested in `arrays` or `shapes`. This would just create way to many snapshots and should be handled manually (or, better yet, strive to make your component props as flat as possible). I'm open to a settings option to allow for this in future iterations, though.
- Test _functionality_ for you. You should still write manual tests for things like button clicks, component state changes, etc.
- Save time _running_ tests. It's only supposed to save time _writing_ tests.
## How
1. Finds and parses your component's source `.jsx` file with [react-docgen](https://github.com/reactjs/react-docgen).
2. Parses your `Component.propTypes` tree and checks for different conditions (required vs optional props, boolean props, etc).
3. Generates fixtures and tests based on the data above.
#### Install
`yarn add jest-auto-snapshots --dev`
or
`npm i jest-auto-snapshots --save-dev`
## Example
#### `MyComponent.jsx`
```js
const MyComponent = ({ stringProp, booleanProp, nodeProp }) => (
{booleanProp && Hello}
{stringProp}
{nodeProp}
);
MyComponent.propTypes = {
booleanProp: PropTypes.bool,
stringProp: PropTypes.string,
nodeProp: PropTypes.node,
};
```
#### `MyComponent.test.js`
```js
import snap from 'jest-auto-snapshots';
import MyComponent from '../MyComponent';
snap(MyComponent, '../MyComponent.jsx');
```
#### `MyComponent.test.js.snap` (generated from the example code above)
```js
// Jest Snapshot v1, https://goo.gl/fbAQLP
exports[`when boolean prop "booleanProp" is set to: "false" 1`] = `
jest-auto-snapshots String Fixture
`;
exports[`when passed all props 1`] = `
Hello
jest-auto-snapshots String Fixture
`;
exports[`when passed only required props 1`] = `
jest-auto-snapshots String Fixture
`;
```
## More Examples
For more examples highlighting different use cases, please check out the [examples directory](https://github.com/icd2k3/jest-auto-snapshots/tree/master/examples)
## API
```js
snap(
component: ,
componentFilePath: , // jest-auto-snapshots needs to parse the component file itself to determine prop fixtures
config: , // optionally set fixtures for the component tests (see Config section below)
);
```
## Config
There are 2 ways to change configuration for the script. Either at the root level in your [jest setup file](https://facebook.github.io/jest/docs/en/configuration.html#setupfiles-array) or in each individual test. The params are the same for both:
Key | Description | Defaults
--- | --- | ---
fixturesByPropKey | Inject component prop fixtures bassed on the prop _key_ | None
fixturesByPropType | Inject component prop fixtures based on the prop _type_ | [see src/configure.js](https://github.com/icd2k3/jest-auto-snapshots/blob/master/src/configure.js). By default it covers all the core [propTypes](https://github.com/facebook/prop-types).
#### Set Config at the Root Level
In your [jest setup file](https://facebook.github.io/jest/docs/en/configuration.html#setupfiles-array):
```js
const jestAutoSnapshots = require('jest-auto-snapshots');
jestAutoSnapshots.configure({
fixturesByPropType: {
customPropType: 'custom fixture',
},
fixturesByPropKey: {
user: { name: 'Joe', age: 30 },
},
});
```
For the above example:
- `'custom fixture'` will be injected for _all_ components with `something: customPropType` in their `propTypes` object.
- `{name: 'Joe', age: 30}` will be injected for _all_ components with `user: PropTypes.shape({ /* ... */ })` in their `propTypes` object.
#### Set Config at the Test Level
In your test file:
```js
import snap from 'jest-auto-snapshots';
import CustomProps from '../CustomProps';
snap(CustomProps, '../CustomProps.jsx', {
fixturesByPropType: {
customPropType: 'custom fixture',
},
fixturesByPropKey: {
user: { name: 'Joe', age: 30 },
},
});
```
For the above example, these custom fixtures will _only_ be injected for the current test.