jest-launchdarkly-mock/README.md

Easily unit test LaunchDarkly feature flagged components with jest

# jest-launchdarkly-mock

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> **Easily unit test LaunchDarkly feature flagged components with jest** :clap:

This package is only compatible with the react sdk.

## Installation

```bash
yarn add -D jest-launchdarkly-mock
```

or

```bash
npm install jest-launchdarkly-mock --save-dev
```

Then in `jest.config.js` add jest-launchdarkly-mock to setupFiles: 

```js
// jest.config.js
module.exports = {
  setupFiles: ['jest-launchdarkly-mock'],
}
```

## Usage
Use the only 3 apis for test cases:

* `mockFlags(flags: LDFlagSet)`: mock flags at the start of each test case. Only mocks
flags returned by the `useFlags` hook.

* `ldClientMock`: a jest mock of the [ldClient](https://launchdarkly.github.io/js-client-sdk/interfaces/_launchdarkly_js_client_sdk_.ldclient.html). All
methods of this object are jest mocks.

* `resetLDMocks` : resets both mockFlags and ldClientMock.

## Example
```tsx
import { mockFlags, ldClientMock, resetLDMocks } from 'jest-launchdarkly-mock'

describe('button', () => {
  beforeEach(() => {
    // reset before each test case
    resetLDMocks()
  })

  test('flag on', () => {
      // arrange
      // You can use the original unchanged case, kebab-case, camelCase or snake_case keys.
      mockFlags({ devTestFlag: true })
  
      // act
      const { getByTestId } = render(<Button />)

      // assert
      expect(getByTestId('test-button')).toBeTruthy()
    })

  test('identify', () => {
    // arrange
    mockFlags({ 'dev-test-flag': true })
    
    // act
    const { getByTestId } = render(<Button />)
    fireEvent.click(getByTestId('test-button'))

    // assert: identify gets called
    expect(ldClientMock.identify).toBeCalledWith({ key: 'aa0ceb' })
  })
})

```