docker container of api not accessible from another container of docker-compose

I have a docker-compose with flask app and some tests written in python to test the api. The api is working fine but the containers with the tests return this error :
equests.exceptions.ConnectionError: HTTPConnectionPool(host=’my_api’, port=5000): Max retries exceeded with url: /Authorization (Caused by NewConnectionError(‘<urllib3.connection.HTTPConnection object at 0x7f02ff5abf10>: Failed to establish a new connection: [Errno 111] Connection refused’)).

here is my docker-compose.yml :

version: "3.9"

networks:
  app_subnet:
    external: true
    

services:
       api:
         image: my_api
         container_name: my_api
         networks:
              app_subnet :
                    ipv4_address: 172.16.0.10
         ports:
              - "5000:5000"
              #- target: 5000
               # published: 5000
               # protocol: tcp
               # mode: host
       
       authentication:
          image: authentication
          depends_on:
              - api
          container_name: authentication_test
          networks:
                    - app_subnet 
                        
          volumes:
              - /home/oussama/Downloads/projet2/:/home/


volumes:
  shared_volume:
       name: shared_volume
       driver: local
       driver_opts:
              type: 'none'
              o: 'bind'
              device: '/home/oussama/Downloads/projet2'

one of the tests that i am running :

import os
import requests

# définition de l'adresse de l'API
api_address = 'my_api'
# port de l'API
api_port = 5000


r = requests.get(
    url='http://{address}:{port}/Authorization'.format(address=api_address, port=api_port),
    headers= {
        'Authorization': 'alice=wonderland'
        }
)

output = '''
============================
    Authentication test
============================

request done at "/Authorization"
| username="alice"
| password="wonderland"

expected result = 200
actual restult = {status_code}

==>  {test_status}

'''


# statut de la requête
status_code = r.status_code

# affichage des résultats
if status_code == 200:
    test_status = 'SUCCESS'
else:
    test_status = 'FAILURE'
print(output.format(status_code=status_code, test_status=test_status))

the api is working after the docker-compose and i get the results that i want with curl command on the port 5000. I checked and no other process is using this port. I tried to change the api_adress in the test code to the ipv4_address that i fixed in the yml file or used the api container_name directly and both times i have the same error : Failed to establish a new connection: [Errno 111] Connection refused’

Any ideas please ?