Once you have spun up docker compose with docker-compose up. You can then open an interactive session to work within the boutique-service container, with docker-compose exec boutique_service bash.
From here you can simply run npm test and interact with the service as if it was on your local machine.
There are a couple of options, but it is probably cleanest to run the npm install from inside the boutique-service docker container.
Once you have spun up docker compose with docker-compose up. You can then open an interactive session to work within the boutique-service container, with docker-compose exec boutique_service bash.
From here you can simply run npm install and interact with the service as if it was on your local machine.