With Jest, is there a way to mock a promise that never resolves? I want to write a snapshot test where I verify my UI in a loading state. The loading state depends on a promise. If the promise resolves, the loading state goes away.

Template:

<div v-if="isLoading">
  <div>Starting service, please wait</div>
</div>

Script:

async startService() {
    try {
      this.isLoading = true;
      const response = await this.service.start();
      this.isLoading = false;
    }

Proposed test:

it('loading screen should display', async() => {
  const startServiceSpy = jest
    .spyOn(Service.prototype, 'start')
    .mockImplementation(() =>
      DO NOT RESOLVE SERVICE CALL HERE
    }));

  wrapper.vm.startService();

  // show loading screen in snapshot
  expect(wrapper.html()).toMatchSnapshot();

});