Mock Test with jest.spyOn and mockRestore

mock_jest_spyOn_restore.test.js

import * as app from "./app";
import * as math from "./math";

test("calls math.add", () => {
  const addMock = jest.spyOn(math, "add");

  // override the implementation
  addMock.mockImplementation(() => "mock");
  expect(app.doAdd(1, 2)).toEqual("mock");

  // restore the original implementation
  addMock.mockRestore();
  expect(app.doAdd(1, 2)).toEqual(3);
});