A replacement flask test client that allows easy JSON API testing

json_test_client.py

import json

from flask.testing import FlaskClient
from flask.wrappers import Response


class JSONResponseWrapper(Response):
    """Extends the BaseResponse to add a get_json method.

    This should be used as the response wrapper in the TestClient.
    """

    def get_json(self):
        """Return the json decoded content."""
        return json.loads(self.get_data(as_text=True))


class JSONTestClient(FlaskClient):
    """Extends the FlaskClient request methods by adding json support.

    This should be used like so::

        app.test_client_class = JSONTestClient
        client = app.test_client()
        client.post(url, json=data)

    Note that this class will override any response_wrapper you wish to use.
    """

    def __init__(self, *args, **kwargs):
        """This ensures the response_wrapper is JSONResponseWrapper."""
        super(JSONTestClient, self).__init__(args[0], response_wrapper=JSONResponseWrapper, **kwargs)

    def open(self, *args, **kwargs):
        json_data = kwargs.pop('json', None)
        if json_data is not None:
            if 'data' in kwargs:
                raise ValueError('Use either `json` or `data`, not both.')

            if 'content_type' not in kwargs:
                kwargs['content_type'] = 'application/json'
            kwargs['data'] = json.dumps(json_data)

        return super(JSONTestClient, self).open(*args, **kwargs)

This is not actual anymore since Flask has the same functionality now.

json – If given, this is serialized as JSON and passed as data. Also defaults content_type to application/json.
http://flask.pocoo.org/docs/1.0/api/#flask.Flask.test_request_context

Changed in version 1.0: JSON support is added to the response, like the request. This is useful when testing to get the test client response data as JSON.
http://flask.pocoo.org/docs/1.0/api/#flask.Response

flask.pocoo.org domain not working anymore, the new one is https://flask.palletsprojects.com