compose.yaml

services:
  app:
     image: app-without-curl-inside
     # app is running a webserver on 8080
     
  app-health:
     image: curl
     command: sleep infinity
     network_mode: "service:app"
     healthcheck:
       test: curl localhost:8080/heath # actually testing pp
       
  foo:
    depends_on:
      - service: app-health
        condition: service_healthy

app-health need to be running, so the sleep infinity command