Great, you pretty much nailed it! There are some minor clean ups possible but that's fine. Are you running prettier? I should probably add a npm script for this.

As for the checks yes that's a good point which I should explain a bit better. The checks are basically type-checking unit tests and makes sure we don't create any regressions with the types. With all the advanced typings going on it's very easy to make a mistake and get an any somewhere. Regular runtime unit tests don't really cover this so we use dts-jest. https://www.npmjs.com/package/dts-jest

It would be nice to get at least one check in to see the return type of the truncate query. I'm assuming this should be a number. The delete check is actually very similar (and simple), so you could try and copy that one. What do you think?

It looks like the tests etc aren't running on this branch yet so I have some work to do. I'll get this sorted in the next couple of days.

Good stuff!