How to unit test a POST method in python?

Question

I have a method that sends a POST containing a JSON to an Elasticsearch instance. I am trying to write a unit test that verify the contents of the sent JSON, but I am not sure how to go about that. Should I create a local server in python and have it verify the contents of the POST or something else? I currently have this:

class TestAnalytics(BaseTest):

    def test_post(self):
        info = {"test1": "value1", "test2": "value2"}
        resp = requests.post(config.tool_repo_urls['es_url'], data=json.dumps(info), headers={'Content-Type': 'application/json'})
        assert_equal(resp.status_code, 200)  # verify valid response code

Answer 1

Creating a local server would be an overkill, what you can do is use unitest library to patch the post() method so it sends the data to your internal assertion method using patch method here is the link https://docs.python.org/3/library/unittest.mock-examples.html. You should look at section 27.6.2. Patch Decorators

Example:

class TestAnalytics(BaseTest):

    @patch('requests.post')
    def test_post(self,mock_post):
        info = {"test1": "value1", "test2": "value2"}
        resp = requests.post(config.tool_repo_urls['es_url'], data=json.dumps(info), headers={'Content-Type': 'application/json'})
        #Some checks done on mock_post object

Full working example below EDIT:

import json

from unittest import TestCase
from unittest.mock import patch

import requests


class TestAnalytics(TestCase):

    @patch('requests.post')
    def test_post(self, mock_post):
        info = {"test1": "value1", "test2": "value2"}
        resp = requests.post("www.someurl.com", data=json.dumps(info), headers={'Content-Type': 'application/json'})
        mock_post.assert_called_with("www.someurl.com", data=json.dumps(info), headers={'Content-Type': 'application/json'})


TestAnalytics().test_post()

Method assert_called_with checks if the patched method was called exactly with the parameters specified in its invocation. In this case it is True

Changing it to for example:

mock_post.assert_called_with("www.someurl.com", data=json.dumps(info))

Will give:

AssertionError: Expected call: post('www.someurl.com', data='{"test1": "value1", "test2": "value2"}')
Actual call: post('www.someurl.com', data='{"test1": "value1", "test2": "value2"}', headers={'Content-Type': 'application/json'})

You can also use the mock_post object to check indvidiual parametrs please check the link above for the full specs of what MagicMock can do

EDIT2

Recently found out about this little library for unit testing requests

https://github.com/getsentry/responses

Answer 2

If you want to verify the sent JSON you should try json.loads(), which will throw a ValueError if the input you pass can't be decoded as JSON.