They run the whole testsuite on the transpiled code. I think.
But yeah it does give me a little shiver to think you are transpiling C code to go code, and the go-code is not really "pure go", but has a platform-dependent unsafe operations. Just look at the repo
My understanding is that the full test suite is actually proprietary and it's part of how sqlite is funded — the maintainers can provide better claims. There is a public test suite but it's a subset of what they do.
https://www.sqlite.org/testing.html