Using the Mocker

The mocker is a loading mechanism to ensure the adapter is correctly in place to intercept calls from requests. Its goal is to provide an interface that is as close to the real requests library interface as possible.

requests_mock.Mocker takes two optional parameters:

real_http (bool):
 If True then any requests that are not handled by the mocking adapter will be forwarded to the real server (see Real HTTP Requests), or the containing Mocker if applicable (see Nested Mockers). Defaults to False.
session (requests.Session):
 If set, only the given session instance is mocked (see Mocking specific sessions).

Activation

Loading of the Adapter is handled by the requests_mock.Mocker class, which provides two ways to load an adapter:

Context Manager

The Mocker object can work as a context manager.

>>> import requests
>>> import requests_mock

>>> with requests_mock.Mocker() as m:
...     m.get('http://test.com', text='resp')
...     requests.get('http://test.com').text
...
'resp'

Decorator

Mocker can also be used as a decorator. The created object will then be passed as the last positional argument.

>>> @requests_mock.Mocker()
... def test_function(m):
...     m.get('http://test.com', text='resp')
...     return requests.get('http://test.com').text
...
>>> test_function()
'resp'

If the position of the mock is likely to conflict with other arguments you can pass the kw argument to the Mocker to have the mocker object passed as that keyword argument instead.

>>> @requests_mock.Mocker(kw='mock')
... def test_kw_function(**kwargs):
...     kwargs['mock'].get('http://test.com', text='resp')
...     return requests.get('http://test.com').text
...
>>> test_kw_function()
'resp'

Contrib

The contrib module also provides ways of loading the mocker based on other frameworks. These will require additional dependencies but may provide a better experience depending on your tests setup.

See Additional Loading for these additions.

Class Decorator

Mocker can also be used to decorate a whole class. It works exactly like in case of decorating a normal function. When used in this way they wrap every test method on the class. The mocker recognise methods that start with test as being test methods. This is the same way that the unittest.TestLoader finds test methods by default. It is possible that you want to use a different prefix for your tests. You can inform the mocker of the different prefix by setting requests_mock.Mocker.TEST_PREFIX:

>>> requests_mock.Mocker.TEST_PREFIX = 'foo'
>>>
>>> @requests_mock.Mocker()
... class Thing(object):
...     def foo_one(self, m):
...        m.register_uri('GET', 'http://test.com', text='resp')
...        return requests.get('http://test.com').text
...     def foo_two(self, m):
...         m.register_uri('GET', 'http://test.com', text='resp')
...         return requests.get('http://test.com').text
...
>>>
>>> Thing().foo_one()
'resp'
>>> Thing().foo_two()
'resp'

This behavior mimics how patchers from mock library works.

Methods

The mocker object can be used with a similar interface to requests itself.

>>> with requests_mock.Mocker() as mock:
...     mock.get('http://test.com', text='resp')
...     requests.get('http://test.com').text
...
'resp'

The following functions exist for the common HTTP methods:

  • delete()
  • get()
  • head()
  • options()
  • patch()
  • post()
  • put()

As well as the basic:

  • request()
  • register_uri()

These methods correspond to the HTTP method of your request, so to mock POST requests you would use the post() function. Further information about what can be matched from a request can be found at Request Matching

Real HTTP Requests

If real_http is set to True then any requests that are not handled by the mocking adapter will be forwarded to the real server, or the containing Mocker if applicable (see Nested Mockers).

>>> with requests_mock.Mocker(real_http=True) as m:
...     m.register_uri('GET', 'http://test.com', text='resp')
...     print(requests.get('http://test.com').text)
...     print(requests.get('http://www.google.com').status_code)  
...
'resp'
200

New in 1.1

Similarly when using a mocker you can register an individual URI to bypass the mocking infrastructure and make a real request. Note this only works when using the mocker and not when directly mounting an adapter.

>>> with requests_mock.Mocker() as m:
...     m.register_uri('GET', 'http://test.com', text='resp')
...     m.register_uri('GET', 'http://www.google.com', real_http=True)
...     print(requests.get('http://test.com').text)
...     print(requests.get('http://www.google.com').status_code)  
...
'resp'
200

Nested Mockers

New in 1.8

When nesting mockers the innermost Mocker replaces all others. If real_http is set to True, at creation or for a given resource, the request is passed to the containing Mocker. The containing Mocker can in turn:

  • serve the request;
  • raise NoMockAddress;
  • or pass the request to yet another Mocker (or to the unmocked requests.Session) if real_http is set to True.
>>> url = "https://www.example.com/"
>>> with requests_mock.Mocker() as outer_mock:
...     outer_mock.get(url, text='outer')
...     with requests_mock.Mocker(real_http=True) as middle_mock:
...         with requests_mock.Mocker() as inner_mock:
...             inner_mock.get(url, real_http=True)
...             print(requests.get(url).text)  
...
'outer'

Most of the time nesting can be avoided by making the mocker object available to subclasses/subfunctions.

Warning

When starting/stopping mockers manually, make sure to stop innermost mockers first. A call from an active inner mocker with a stopped outer mocker leads to undefined behavior.

Mocking specific sessions

New in 1.8

requests_mock.Mocker can be used to mock specific sessions through the session parameter.

>>> url = "https://www.example.com/"
>>> with requests_mock.Mocker() as global_mock:
...     global_mock.get(url, text='global')
...     session = requests.Session()
...     print("requests.get before session mock:", requests.get(url).text)
...     print("session.get before session mock:", session.get(url).text)
...     with requests_mock.Mocker(session=session) as session_mock:
...         session_mock.get(url, text='session')
...         print("Within session mock:", requests.get(url).text)
...         print("Within session mock:", session.get(url).text)
...     print("After session mock:", requests.get(url).text)
...     print("After session mock:", session.get(url).text)
...
'requests.get before session mock: global'
'session.get before session mock: global'
'requests.get within session mock: global'
'session.get within session mock: session'
'requests.get after session mock: global'
'session.get after session mock: global'

Note

As an alternative, requests_mock.Adapter instances can be mounted on specific sessions (see Adapter Usage).