Platform for test doubles in Python (mocks, stubs, Spy, and dummies)
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Welcome to ludibrio



Ludibrio is registered with PyPi. If you have pip, setuptools or Distribute you can install mock with:

$ sudo easy_install ludibrio


The latest official version is 3.0.2. Here’s how to get it:

Getting involved !

Ludibrio's development may be viewed and followed on github:

Retrieve the source code using 'git':

$ git clone git://

Install package in 'development mode' and run tests with doctestcommand

$ sudo easy_install doctestcommand
$ git clone git://
$ cd ludibrio
$ sudo python develop
$ cd ludibrio
$ doctest

In a nutshell

Test doubles are fake objects that simulate the behavior of a real object for testing purposes.


Mocks are objects pre-programmed with expectations which form a specification of the calls they are expected to receive:

>>> from ludibrio import Mock
>>> with Mock() as MySQLdb:
...     con = MySQLdb.connect('server', 'user', 'XXXX')
...     con.select_db('DB') >> None
...     cursor = con.cursor()
...     cursor.execute('select * from numbers') >> None
...     cursor.fetchall() >> [1,2,3,4,5]
>>> con = MySQLdb.connect('server', 'user', 'XXXX')
>>> con.select_db('DB')
>>> cursor = con.cursor()
>>> cursor.execute('select * from numbers')
>>> cursor.fetchall()
[1, 2, 3, 4, 5]

>>> MySQLdb.validate() #passed


Stubs provide pre-defined answers to method calls made during a test:

>>> from ludibrio import Stub
>>> with Stub() as x:
...     x.anything() >> 'response'
>>> x.anything()

Trivial mocking or stubing for any external module

Ludibrio also offers a replace mode, which basically means if a "from ... import ..." statement is defined into a 'with' scope, the replay mechanism will return a mock object to replace the original object in namespace of the whole Python interpreter (including any modules, etc). There's a simple example below to illustrate how use it:

>>> from ludibrio import Stub

>>> with Stub() as time:
...     from time import time
...     time() >> 171
>>> from time import time
>>> time()


Two Ludibrio's powerful features that aren't found in other mocking systems is the ability of proxying existing objects, or patching a real instance or class.

When an object is proxied, Ludibrio create a Test Double object holding a reference to the real object, allowing expressions passthrough to it(mocked or not, and by default or on request):

>>> from os.path import splitext
>>> with Stub(proxy=splitext) as splitext:
...     splitext('ludibrio/') >> ('/temp/temp','.temp')
>>> splitext('')
('mock', '.py')
>>> splitext('ludibrio/')
('/temp/temp', '.temp')