Test functions cannot both take a ‘done’ callback

You are combining Async/Await and Done.

Either use asnyc/await, or done.

it('throws an error if user signs up with email that is in use', async () => {
    try {
        await service();
        expect(...);
    } catch (err) {
    }
});

or use the done format

it('throws an error if user signs up with email that is in use', (done) => {
    ...
    service()
     .then( ...) {}
     .catch( ...) {}
    }
    done();
});