Can't run pytestrequests tests for Flask app inside Docker

My setup –

project/
    app.py
    test_hello.py
    test/
    Dockerfile
    requirements.txt

app.py body is

from flask import Flask

app = Flask(__name__)


@app.route('/hello')
def privet():
    return 'hello bob'


if __name__ == '__main__':
    app.run(debug=True)

test_hello.py body is

import requests


def test_hello():
    session = requests.Session()
    session.trust_env = False
    s = session.get('http://localhost:5000/hello').text
    assert s == 'hello bob'

Dockerfile is

# syntax=docker/dockerfile:1

FROM python:3.7-alpine
WORKDIR /code
ENV FLASK_APP=app
ENV FLASK_RUN_HOST=0.0.0.0
COPY requirements.txt requirements.txt
RUN pip3 install -r requirements.txt
EXPOSE 5000
COPY . .
CMD ["flask", "run"]
CMD ["pytest"]

When I’m launching test locally on my machine – Everything is OK

But when I’lauching test on Docker container (after building image and running container) – I’m getting error from requests:

requests.exceptions.ConnectionError: HTTPConnectionPool(host='localhost', port=5000): Max retries exceeded with url: /hello (Caused by NewConnectionError('<urllib3.connection.HTTPConnection object at 0x7fbcacb07c90>: Failed to establish a new connection: [Errno 111] Connection refused'))

/usr/local/lib/python3.7/site-packages/requests/adapters.py:516: ConnectionError

Could anyone please tell me what is wrong? Awesome thanks