DI Purist 3

test.js

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

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