Using requests-mock to Simulate HTTP Requests in Python Unit Tests

requests-mock is a Python library that allows you to mock HTTP requests made with the requests library, making unit and integration tests faster and more reliable by avoiding real external API calls.

Install the library via pip:

pip install requests-mock

1. Simple GET request mock

import requests
import requests_mock

def test_simple_get():
    with requests_mock.Mocker() as m:
        m.get('http://test.com/api/v1/users', text='{"users":[]}')
        response = requests.get('http://test.com/api/v1/users')
        assert response.text == '{"users":[]}'

test_simple_get()

2. POST request mock and verify request body

def test_post_request():
    with requests_mock.Mocker() as m:
        m.post('http://test.com/api/v1/users', text='User created', status_code=201)
        response = requests.post('http://test.com/api/v1/users', json={'username': 'testuser'})
        assert m.last_request.json() == {'username': 'testuser'}
        assert response.text == 'User created'

test_post_request()

3. Mock different status code response

def test_status_code():
    with requests_mock.Mocker() as m:
        m.get('http://test.com/api/v1/resource', status_code=404)
        response = requests.get('http://test.com/api/v1/resource')
        assert response.status_code == 404

test_status_code()

4. Use regular expression to match URLs

import re

def test_regex_url():
    with requests_mock.Mocker() as m:
        m.get(re.compile(r'http://test.com/api/v1/users/\d+'), text='User details')
        response = requests.get('http://test.com/api/v1/users/123')
        assert response.text == 'User details'

test_regex_url()

5. Multiple calls with different responses

def test_multiple_responses():
    with requests_mock.Mocker() as m:
        m.get('http://test.com/api/v1/toggle', [{'text': 'On'}, {'text': 'Off'}])
        response1 = requests.get('http://test.com/api/v1/toggle')
        response2 = requests.get('http://test.com/api/v1/toggle')
        assert response1.text == 'On'
        assert response2.text == 'Off'

test_multiple_responses()

6. Mock JSON response

def test_json_response():
    with requests_mock.Mocker() as m:
        m.get('http://test.com/api/v1/config', json={'key': 'value'})
        response = requests.get('http://test.com/api/v1/config')
        assert response.json()['key'] == 'value'

test_json_response()

7. Handle HEAD request

def test_head_request():
    with requests_mock.Mocker() as m:
        m.head('http://test.com/api/v1/check', headers={'ETag': '123abc'})
        response = requests.head('http://test.com/api/v1/check')
        assert response.headers['ETag'] == '123abc'

test_head_request()

8. Simulate exceptions

def test_exception():
    with requests_mock.Mocker() as m:
        m.get('http://test.com/api/v1/error', exc=requests.exceptions.HTTPError)
        try:
            requests.get('http://test.com/api/v1/error')
        except requests.exceptions.HTTPError:
            assert True
        else:
            assert False

test_exception()

9. Mock request with query parameters

def test_query_params():
    with requests_mock.Mocker() as m:
        m.get('http://test.com/api/v1/search', text='Search results', params={'query': 'python'})
        response = requests.get('http://test.com/api/v1/search', params={'query': 'python'})
        assert response.text == 'Search results'

test_query_params()

10. Mock redirect response

def test_redirect():
    with requests_mock.Mocker() as m:
        m.get('http://test.com/api/v1/redirect', status_code=302, headers={'Location': 'http://test.com/api/v1/newpath'})
        response = requests.get('http://test.com/api/v1/redirect', allow_redirects=True)
        assert response.url.endswith('/api/v1/newpath')

test_redirect()