element-web-Github/test/jest-mocks.js

// https://jestjs.io/docs/en/manual-mocks#mocking-methods-which-are-not-implemented-in-jsdom
Object.defineProperty(window, 'matchMedia', {
    writable: true,
    value: jest.fn().mockImplementation(query => ({
        matches: false,
        media: query,
        onchange: null,
        addListener: jest.fn(), // deprecated
        removeListener: jest.fn(), // deprecated
        addEventListener: jest.fn(),
        removeEventListener: jest.fn(),
        dispatchEvent: jest.fn(),
    })),
});