Why can't my container communicate with postgres?

Question

Docker

docker-compose.test.yml:

version: '3'

services:
  db:
    image: postgres
  web:
    restart: always
    image: $CONTAINER_TEST_IMAGE
    command: python3 manage.py test --noinput
    depends_on:
    - db

.gitlab-ci.yml:

...
test:
  stage: test
  script:
    - docker pull $CONTAINER_TEST_IMAGE
    - docker-compose -f docker-compose.test.yml run web
    - docker-compose rm -f web
  tags:
    - dev
...

Mistake:

could not connect to server: Connection refused
  Is the server running on host "db" (172.22.0.2) and accepting
  TCP/IP connections on port 5432?

What's the catch, if I restart Pipeline in gitlab, everything works as it should.