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

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.