Yeah, the test suite seems pretty key. It also probably contains information about the proprietary extensions and contract work from clients and can likely never be released.

Proprietary test suite is a pretty interesting strategy actually. Very difficult for others to just steal your code and support effort and run if they have to start from zero to build a massive test suite.

I wonder how difficult it would be for some sort of tool to assume a particular original sqlite.c has full coverage and then suggest where additional tests are needed for patches?