Scheduling integrations do not usually break on the first request. They break after the booking exists. The user gets an email. The host has Google Calendar connected. Your app sends its own ICS file. Then somebody reschedules or cancels and suddenly there are two calendar events, or one event refuses to disappear. That is not a generic "calendar APIs are hard" problem. It is a workflow identity problem. The specific workflow The narrow Cal.com flow I care about is: Get available slots Create a booking Fetch the booking Reschedule it Cancel it Verify the calendar and webhook side effects still point at the same booking In API terms, the happy path looks like this: GET /v2/slots POST /v2/bookings GET /v2/bookings/{bookingUid} POST /v2/bookings/{bookingUid}/reschedule POST /v2/bookings/{bookingUid}/cancel Enter fullscreen mode Exit fullscreen mode That is the test.…