The js original file is copied from the jQuery project, it could be any js file. Then I created gzipped and brotli compressed copies locally.
The css file is copied out of google.com, it could be any css file.
The nginx.conf file is as minimal as I could make it.
The Dockerfile is based on an nginx image with brotli compiled in, the rest is copying the test files into it.
You can test with this:
docker build -t nb .
docker run -d --rm --name nb -p 8888:80 nb
# js files (works as expected)
curl -svo /dev/null -H 'Accept-Encoding:foo' localhost:8888/jquery.js
curl -svo /dev/null -H 'Accept-Encoding:deflate,gzip' localhost:8888/jquery.js
curl -svo /dev/null -H 'Accept-Encoding:deflate,gzip,br' localhost:8888/jquery.js
# css files
curl -svo /dev/null -H 'Accept-Encoding:foo' localhost:8888/google.css
curl -svo /dev/null -H 'Accept-Encoding:deflate,gzip' localhost:8888/google.css
# doesn't work as expected: it does not gzip
curl -svo /dev/null -H 'Accept-Encoding:deflate,gzip,br' localhost:8888/google.css