How to test watchers in vue

vue-test-watchers.js

it("calls #loadCities if the zipCode is correct and there are 1+ chars in the field", async () => {
  // This is how to test watchers:
  // 1. set the starting data if neccessary
  wrapper.setData({ searchTermCity: "", address: { zipCode: "12345" } });
  // 2. Change the current value
  wrapper.vm.searchTermCity = "Ha";
  // 3. Manually trigger watcher since vue-test-utils doesn't do that anymore:(
  wrapper.vm._watchers.find(w => w.expression === "searchTermCity").run();
  expect(wrapper.vm.loadCities).toHaveBeenCalledWith("Ha");
});