DI Pragmatic 3

test.js

const mockUpdate = jest.fn();

jest.mock("./repos/user.js", () => () => ({
  update: mockUpdate;
}));

jest.beforeEach(() => jest.restoreAllMocks());

const updateUserPreference = require("./use-cases/update-user-preference.js");

it("updates the user preference", () => {
  updateUserPreference({ key: "someKey", value: "someValue" });
  expect(mockUpdate).toHaveBeenCalledWith(/* the updatedUser */);
});