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Jest integration

Async Storage module is tightly coupled with its NativeModule part - it needs a running React Native application to work properly. In order to use it in tests, you have to provide its separate implementation. Follow these steps to add a mocked Async Storage module.

Using Async Storage mock

You can use one of two ways to provide mocked version of AsyncStorage:

With mocks directory

  1. In your project root directory, create __mocks__/@react-native-async-storage directory.
  2. Inside that folder, create async-storage.js file.
  3. Inside that file, export Async Storage mock.
export default from '@react-native-async-storage/async-storage/jest/async-storage-mock'

With Jest setup file

  1. In your Jest config (probably in package.json) add setup files location:
"jest": {
"setupFiles": ["./path/to/jestSetupFile.js"]
}
  1. Inside your setup file, set up Async Storage mocking:
import mockAsyncStorage from '@react-native-async-storage/async-storage/jest/async-storage-mock';

jest.mock('@react-native-async-storage/async-storage', () => mockAsyncStorage);

Testing with mock

Each public method available from Async Storage is a mock function, that you can test for certain condition, for example, if .getItem has been called with a specific arguments:

it('checks if Async Storage is used', async () => {
await asyncOperationOnAsyncStorage();

expect(AsyncStorage.getItem).toBeCalledWith('myKey');
})

Overriding Mock logic

You can override mock implementation, by replacing its inner functions:

// somewhere in your configuration files
import AsyncStorageMock from '@react-native-async-storage/async-storage/jest/async-storage-mock';

AsyncStorageMock.multiGet = jest.fn(([keys], callback) => {
// do something here to retrieve data
callback([]);
})

export default AsyncStorageMock;

You can check its implementation to get more insight into methods signatures.