the testing pyramid is worth knowing about; unit tests double code size and maintenance cost for the unit; I've found unit tests only fit long-lived code and co

the testing pyramid is worth knowing about; unit tests double code size and maintenance cost for the unit; I've found unit tests only fit long-lived code and coverage doesn't generally correlate with reliability of product performance; black box end to end testing at the interface level for the general scenarios does correlate with reliability, for those scenarios; writing tests that properly separate concerns in this way seems to make it easier to write and maintain tests, and the product