We're going to start much the same way. I'm actually going to copy these two lines from generateMessage to the generateLocationMessage test case:

expect(message.createdAt).toBeA('number');
expect(message).toInclude({from, text});

We're expecting the message.createdAt property to be a number which it should be, then we're expecting message to include a from property equal to Deb, and we're going to expect it to have a url property equal to the url string we defined:

describe('generateLocationMessage', () => {
  it('should generate correct location object', () => {
    var from = 'Deb';
    var latitude = 15;
    var longitude = 19;
    var url = 'https://www.google.com/maps?q=15,19';
    var message = generateLocationMessage(from, latitude, longitude);

    expect(message.createdAt).toBeA('number');
    expect(message).toInclude({from, url});
  });
});

If both of these assertions pass then we know the object returned from generateLocationMessage is correct.