The test coverage of sqlite-utils is solid - pytest-cov reports 95% total. The project has 9,973 lines of implementation code and 14,860 of test code.

Here's the delete_where() test: https://github.com/simonw/sqlite-utils/blob/7a52214624ae0e2c...

The problem with the test was that it asserted that the records were deleted inside of the same transaction as the delete, so it missed the changed behavior where the delete didn't commit properly (it had committed properly prior to the new transactions work).