Use HTTP Archive (HAR) files in Python tests

To send this request to an API backend and assert the API response matches this response…

{
  "log": {
    "version": "1.2",
    "entries": [
      {
        "request": {
          "method": "POST",
          "url": "mock://example.com/users/",
          "headers" : [
            {
              "name": "Accept",
              "value": "application/json"
            }
          ],
          "postData": {
            "mimeType": "application/json",
            "text" : {
              "username": "foo_username",
              "email": "foo@example.com",
              "group": "479e75e6-755a-46f1-a949-d6fee3671b3c"
            }
          },
          "comment" : "Test validation errors"
        },
        "response": {
          "status": 201,
          "statusText": "Created",
          "headers" : [
            {
              "name": "Allow",
              "value": "GET, POST, HEAD, OPTIONS"
            },
            {
              "name": "Vary",
              "value": "Accept, Cookie"
            }
          ],
          "content": {
            "mimeType": "application/json",
            "text": {
              "username": "foo_username"
            }
          }
        }
      }
    ]
  }
}

Use this test:

import datetime

# Import the appropriate backend for your framework.
# Currently there are backends for the `requests` library...
from test_har.requests_har as test_har
# and for the Django ReST Framework.
# from test_har.django_rest_har as test_har
# Contributions for other frameworks welcome!

from .. import models


class MyAPITest(test_har.HARTestCase):
    """
    Specify the HAR file to use by default.
    """

    # Path to file relative to this test file
    # Set to `None` to skip automatic HAR parsing and set up
    example_har = 'example.har.json'

    def test_my_response(self):
        """
        Write your test as you would.
        """
        # For convenience, `self.example` is the parsed JSON in
        # `self.example_har`, `self.entry` is the first request/response
        # entry from `log/entries/0` in the HAR., `self.headers` is a
        # dictionary of the response headers for that entry, and
        # `self.content` is the response body content from that entry.

        # Make any changes to the test fixture necessary for the test such
        # as creating related objects before a POST that requires them.
        group = models.Group(
            name='foo_group',
            uuid=self.entry["request"]["postData"]["text"]["group"])

        # Make any changes to the HAR necessary for the assertions to work
        # before sending the requests
        self.content["some_dynamic_value"] = models.my_dynamic_function()

        # Send the HAR requests, assert responses match the HAR, and return
        # the responses.  Currently, assertions are made against the
        # response: `Status` code, `Status` reason text, `Content-Type`
        # MIME type, other headers in the HAR, and the response body
        # content.  If the response MIME type is a JSON type,
        # then assertions will be made against each top-level key
        # individually and ignore any key in the response not included in
        # the HAR.
        now = datetime.datetime.now()
        responses = self.assertHAR(self.example)

        # Make any other assertions, or do anything else you'd like to do,
        # with the responses.
        self.assertAlmostEqual(
            datetime.strptime(response[0].json()['created'], format='...'),
            now, delta=datetime.timedelta(seconds=1),
            msg='Wrong automatic creation time')

    def test_my_other_response(self):
        """
        Test a different HAR file.
        """
        # Replace `self.example` and the other convenience attributes with
        # the content form another HAR file
        self.setUpHAR('other.har.json')
        responses = self.assertHAR(self.example)
        ...