Snapshot testing saves a copy of an expected output inside a repo, and asserts
that the System Under Test always produces a matching copy.
[`insta`](https://docs.rs/insta), the snapshot testing library we use stores
snapshots in this folder.
This allows us to regression-test and review changes to our autogenerated
OpenRPC definitions.
If you're making changes to OpenRPC files, review is easier with
```console
$ cargo install cargo-insta
...
$ cargo insta review
```
See also <https://insta.rs/docs/quickstart/>.