Looks like this post got shadow-flagged or somehow removed from the main listing. It's still on new, but not in any of the first 5 top pages, after being on the front page earlier.
If anyone on mixpanel is reading this I would love to know how do they maintain mocks? We've been burnt so many times with outdated mocks in my experience that I've always tried to supplement our front-end tests with Selenium as they run against a real server.
Our experience is that Cypress is the best tool out there in terms of better integration with CI tools even though it's not stable yet. We also connect to our cross-origin staging servers because it feels more e2e to us.