The library supports mocking the storage in memory to support read/write during tests. Follow the guide below to make it work with jest.
Add mmkvJestSetup.js and transformIgnorePatterns in jest.config.js.
module.exports = {
preset: 'react-native',
setupFiles: [
'./node_modules/react-native-mmkv-storage/jest/mmkvJestSetup.js',
],
transformIgnorePatterns: ['/!node_modules\\/react-native-mmkv-storage/'],
};You will need to mock the storage when your tests run as follows:
import 'react-native';
import MMKVStorage, {isLoaded} from 'react-native-mmkv-storage'; // Import the library as normal.
describe('MMKV Storage mock functionality', () => {
beforeEach(function () {
// Install the in-memory adapter
let mmkvMock = require('react-native-mmkv-storage/jest/dist/jest/memoryStore.js');
mmkvMock.unmock(); // Cleanup if already mocked
mmkvMock.mock(); // Mock the storage
});
// Use the storage methods as needed. Everything is mocked now
it('Mock bindings are installed', () => {
expect(isLoaded()).toBe(true);
});
it('Init an instance', () => {
let instance = new MMKVStorage.Loader().initialize();
expect(instance.instanceID).toBe('default');
expect(instance.getString('unknown')).toBe(null);
});
});