Thanks for tackling this new resource! That's a lot of snapshot tests! 🎉 I have one comment regarding modifying generated code, and some other minor ones.

We're covering a lot of ground here, and explicitly validating the location type when creating DocumentationPart. We could also add a note that we're not covering the whole validation of the location (and adding the link below), as it seems to be very extensive, and it's outside of the scope for now, see https://docs.aws.amazon.com/apigateway/latest/api/API_DocumentationPartLocation.html
There are a lot of different cases, depending on each other, well, it's a lot, and we don't need that. Thanks for tackling the location type validation for now 😄

Thanks again for separating the tests into a class, and writing so many! 🎉

LGTM! 🚀 awesome set of changes, thanks for quickly working on the comments! Really awesome to see it thoroughly validated. Thank you!