import vcr
import urllib.request

with vcr.use_cassette('fixtures/vcr_cassettes/synopsis.yaml'):
    response = urllib.request.urlopen('').read()
    assert b'Example domains' in response

Run this test once, and will record the HTTP request to fixtures/vcr_cassettes/synopsis.yaml. Run it again, and will replay the response from when the http request is made. This test is now fast (no real HTTP requests are made anymore), deterministic (the test will continue to pass, even if you are offline, or goes down for maintenance) and accurate (the response will contain the same headers and body you get from a real request).

You can also use as a decorator. The same request above would look like this:

def test_iana():
    response = urllib.request.urlopen('').read()
    assert b'Example domains' in response

When using the decorator version of use_cassette, it is possible to omit the path to the cassette file.

def test_iana():
    response = urllib.request.urlopen('').read()
    assert b'Example domains' in response

In this case, the cassette file will be given the same name as the test function, and it will be placed in the same directory as the file in which the test is defined. See the Automatic Test Naming section below for more details.

Record Modes

VCR supports 4 record modes (with the same behavior as Ruby’s VCR):


  • Replay previously recorded interactions.

  • Record new interactions if there is no cassette file.

  • Cause an error to be raised for new requests if there is a cassette file.

It is similar to the new_episodes record mode, but will prevent new, unexpected requests from being made (e.g. because the request URI changed).

once is the default record mode, used when you do not set one.


  • Record new interactions.

  • Replay previously recorded interactions. It is similar to the once record mode, but will always record new interactions, even if you have an existing recorded one that is similar, but not identical.

This was the default behavior in versions < 0.3.0


  • Replay previously recorded interactions.

  • Cause an error to be raised for any new requests. This is useful when your code makes potentially dangerous HTTP requests. The none record mode guarantees that no new HTTP requests will be made.


  • Record new interactions.

  • Never replay previously recorded interactions. This can be temporarily used to force VCR to re-record a cassette (i.e. to ensure the responses are not out of date) or can be used when you simply want to log all HTTP requests.

Unittest Integration

Inherit from VCRTestCase for automatic recording and playback of HTTP interactions.

from vcr.unittest import VCRTestCase
import requests

class MyTestCase(VCRTestCase):
   def test_something(self):
       response = requests.get('')

Similar to how returns the cassette from the context manager, VCRTestCase makes the cassette available as self.cassette:

self.assertEqual(len(self.cassette), 1)
self.assertEqual(self.cassette.requests[0].uri, '')

By default cassettes will be placed in the cassettes subdirectory next to the test, named according to the test class and method. For example, the above test would read from and write to cassettes/MyTestCase.test_something.yaml

The configuration can be modified by overriding methods on your subclass: _get_vcr_kwargs, _get_cassette_library_dir and _get_cassette_name. To modify the VCR object after instantiation, for example to add a matcher, you can hook on _get_vcr, for example:

class MyTestCase(VCRTestCase):
    def _get_vcr(self, **kwargs):
        myvcr = super(MyTestCase, self)._get_vcr(**kwargs)
        myvcr.register_matcher('mymatcher', mymatcher)
        myvcr.match_on = ['mymatcher']
        return myvcr

See the source for the default implementations of these methods.

If you implement a setUp method on your test class then make sure to call the parent version super().setUp() in your own in order to continue getting the cassettes produced.


In case inheriting from VCRTestCase is difficult because of an existing class hierarchy containing tests in the base classes, inherit from VCRMixin instead.

from vcr.unittest import VCRMixin
import requests
import unittest

class MyTestMixin(VCRMixin):
   def test_something(self):
       response = requests.get(self.url)

class MyTestCase(MyTestMixin, unittest.TestCase):
    url = ''

Pytest Integration

A Pytest plugin is available here : pytest-vcr.

Alternative plugin, that also provides network access blocking: pytest-recording.