I was surprised that the test suit not open source. Some info in https://sqlite.org/testing.html

It looks like some parts are open source and other not. Does anyone know more about the backstory? (It looks like one is a custom program that generate fuzz test. Do they sell it to others SQL engines?)

The CoRecursive episode with SQLite creator D. Richard Hipp goes through it. I've linked to the part of the transcript that covers it, the key quote being:

> We still maintain the first one, the TCL tests. They’re still maintained. They’re still out there in the public. They’re part of the source tree. Anybody can download the source code and run my test and run all those. They don’t provide 100% test coverage but they do test all the features very thoroughly. The 100% MCD tests, that’s called TH3. That’s proprietary. I had the idea that we would sell those tests to avionics manufacturers and make money that way. We’ve sold exactly zero copies of that so that didn’t really work out. It did work out really well for us in that it keeps our product really solid and it enables us to turn around new features and new bug fixes very fast.

https://corecursive.com/066-sqlite-with-richard-hipp/#testin...

it's their business model

it's free

but if you want the compliance paperwork, you pay for it

usefull if you need to validate that the database runs properly on yours embedded platform, possibly with its custom io and sync primitives.