A proof-of-concept start at a Python version of Ruby's VCR library
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This is a proof-of-concept start at a Python version of Ruby's VCR library.

Build Status

What it is supposed to do

Simplify testing by recording all HTTP interactions and saving them to "cassette" files, which are just yaml files. Then when you run your tests again, they all just hit the text files instead of the internet. This speeds up your tests and lets you work offline.

Compatibility Notes

This should work with Python 2.6 and 2.7. There aren't any context managers in 2.5 so I'm not bothering with that.

Currently I've only tested this (a little bit) with urllib2. It's known to NOT WORK with urllib.

How to use it

import vcr
import urllib2

with vcr.use_cassette('fixtures/vcr_cassettes/synopsis.yaml'):
    response = urllib2.urlopen('http://www.iana.org/domains/example/').read()
    assert 'Example Domains' in response

Run this test once, and VCR.py will record the http request to fixtures/vcr_cassettes/synopsis.yml. Run it again, and VCR.py will replay the response from iana.org 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 iana.org goes down for maintenance) and accurate (the response will contain the same headers and body you get from a real request).

Ruby VCR compatibility

I'm not trying to match the format of the YAML files. Cassettes generated by Ruby's VCR are not compatible with VCR.py. The API is similar but VCR.py doesn't have nearly as many features.

Known Issues

  • Probably only works with urllib2. Hey, doesn't requests use urllib2? Maybe that works too then.
  • Loading urls that do a 301/302 redirect don't work
  • I haven't tested PUT/DELETE requests

Similar libraries in Python

Neither of these really implement the API I want, but I have cribbed some code from them.


This library uses the MIT license