All mock functions have this special .mock property, which is where data about how the function has been called and what the function returned is kept. The .mock property also tracks the value of this for each call, so it is possible to inspect this as well: const myMock1 = jest.fn(); const a = new myMock1();. fetch mock for jest. Latest version: 3.0.3, last published: 2 years ago. Start using jest-fetch-mock in your project by running `npm i jest-fetch-mock`. There are 180 other projects in the npm registry using jest-fetch-mock.. "/>Jest mock resizeobserver