Do this and you should be 👌👌👌:
bash script/download-libs.sh
npm ci
npm test
notes - As a developer, you need to run bash script/download-libs.sh to download the FFI libraries prior to running npm install / npm ci as the libraries will be expected to be there, and you won't have any node_modules installed yet.
For end users, the ffi folder is populated, as part of the npm publishing step.