import vcr
import urllib2

with vcr.use_cassette('fixtures/vcr_cassettes/synopsis.yaml'):
    response = urllib2.urlopen('').read()
    assert '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 = urllib2.urlopen('').read()
    assert '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 = urllib2.urlopen('').read()
    assert '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 This can be temporarily used to force VCR to re-record a cassette (i.e. to ensure the responses are not out of date) or can be used when you simply want to log all HTTP requests.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

While it’s possible to use the context manager or decorator forms with unittest, there’s also a VCRTestCase provided separately by vcrpy-unittest.

Pytest Integration

A Pytest plugin is available here : pytest-vcr.

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