How do you balance unit, integration, and end-to-end testing in a frontend project?

Testing a vehicle: checking each individual bolt (unit) is quick and numerous, testing the assembled engine (integration) is less frequent, while taking the entire car for a test drive on the road (e2e) is slow and costly, so it is done the least. The higher the level of testing, the more realistic it becomes, but it also takes more time and is more expensive.