services:
  app:
    image: busybox
    command: ["/bin/busybox", "sh", "-c", "env | grep ZZ"]
    tmpfs:
      - /run
      - /tmp
    env_file:
      - path: ../env-files/project-1.env
      - path: ../env-files/project-3.env # this file is missing
        required: false