react-native-blob-util mock

react-native-blob-util.js

// __mocks__/react-native-blob-util.js

module.exports = {
  __esModule: true,
  default: {
    DocumentDir: jest.fn(),
    config: jest.fn(() => ({
      fetch: jest.fn(() => ({
        progress: jest.fn().mockResolvedValue(true),
      })),
    })),
    fs: {
      cp: jest.fn().mockResolvedValue(true),
      dirs: {
        CacheDir: '/mockCacheDir',
      },
      unlink: jest.fn(),
    },
  },
};

SomeTest.ts

import ReactNativeBlobUtil from 'react-native-blob-util';

describe('SomeTest', () => {
  beforeEach(() => {
    jest.clearAllMocks();
  });

  it('handles errors', () => {
    ReactNativeBlobUtil.config.mockReturnValueOnce({
      fetch: jest.fn().mockReturnValue({
        progress: jest.fn(() =>
          Object.assign(Promise.reject(), { cancel: jest.fn() }),
        ),
      }),
    });
    
    // assertions...
    
  });
});

Derived from https://stackoverflow.com/a/62371311/355512