pact-test

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Pact Test for Python

This repository contains a Python implementation for Pact <http://pact.io/>. Pact is a specification for Consumer Driven Contracts Testing. For further information about Pact project, contracts testing, pros and cons and useful resources please refer to the Pact website <http://pact.io/>.

There are two phases in Consumer Driven Contracts Testing: a Consumer sets up a contract (it's consumer driven after all!), and a Provider honours it. But, before that...

Installation

Pact Test is distributed through `PyPi <https://pypi.python.org/pypi/pact-test>`_ so it can be easily included in the
:code:`requirements.txt` file or normally installed with :code:`pip`:

.. code:: bash

  $ pip install pact-test

Providers Tests (*Set the Contracts*)
-------------------------------------

.. image:: https://img.shields.io/badge/Pact-1.0-brightgreen.svg
    :target: https://github.com/pact-foundation/pact-specification/tree/version-1
.. image:: https://img.shields.io/badge/Pact-1.1-red.svg
    :target: https://github.com/pact-foundation/pact-specification/tree/version-1.1
.. image:: https://img.shields.io/badge/Pact-2.0-red.svg
    :target: https://github.com/pact-foundation/pact-specification/tree/version-2
.. image:: https://img.shields.io/badge/Pact-3.0-red.svg
    :target: https://github.com/pact-foundation/pact-specification/tree/version-3
.. image:: https://img.shields.io/badge/Pact-4.0-red.svg
    :target: https://github.com/pact-foundation/pact-specification/tree/version-4

Consumers run Provider Tests to create pacts and establish a contract between
them and service providers. An example of a Python client using pact test is
available at `here <https://github.com/Kalimaha/PythonEats>`_. Consumers define
all the interactions with their providers in the following way:

.. code:: python

    @service_consumer('PythonEats')
    @has_pact_with('PyzzaHut')
    class PyzzaHutTest(ServiceProviderTest):

        @given('some pizzas exist')
        @upon_receiving('a request for a pepperoni pizza')
        @with_request({'method': 'get', 'path': '/pizzas/pepperoni/'})
        @will_respond_with({'status': 200, 'body': {'id': 42, 'type': 'pepperoni'}})
        def test_get_pepperoni_pizza(self):
            pizza = get_pizza('pepperoni')
            assert pizza['id'] == 42
            assert pizza['type'] == 'pepperoni'

This test verifies, against a mock server, the expected interaction and creates
a JSON file (*the pact*) that will be stored locally and also sent to the
Pact Broker, if available. It is possible to define multiple tests for the same
state in order to verify all the scenarios of interest, For example, we can
test an unhappy :code:`404` situation:

.. code:: python

    @given('some pizzas exist')
    @upon_receiving('a request for an hawaiian pizza')
    @with_request({'method': 'get', 'path': '/pizzas/hawaiian/'})
    @will_respond_with({'status': 404, 'body': {'message': 'we do not serve pineapple with pizza'}})
    def test_get_hawaiian_pizza(self):
        pizza = get_pizza('hawaiian')
        assert pizza.status_code == 404
        assert pizza.json()['message'] == 'we do not serve pineapple with pizza'

Consumers Tests (*Honour Your Contracts*)
-----------------------------------------

.. image:: https://img.shields.io/badge/Pact-1.0-brightgreen.svg
    :target: https://github.com/pact-foundation/pact-specification/tree/version-1
.. image:: https://img.shields.io/badge/Pact-1.1-red.svg
    :target: https://github.com/pact-foundation/pact-specification/tree/version-1.1
.. image:: https://img.shields.io/badge/Pact-2.0-red.svg
    :target: https://github.com/pact-foundation/pact-specification/tree/version-2
.. image:: https://img.shields.io/badge/Pact-3.0-red.svg
    :target: https://github.com/pact-foundation/pact-specification/tree/version-3
.. image:: https://img.shields.io/badge/Pact-4.0-red.svg
    :target: https://github.com/pact-foundation/pact-specification/tree/version-4

Providers run Consumer Tests to verify that they are honouring their pacts with the consumers. There are few examples
of an hypothetical restaurant service implemented with the most popular Python web frameworks:

* Djanjo (*TODO*)
* `Flask <https://github.com/Kalimaha/restaurant-service-flask>`_
* `Pyramid <https://github.com/Kalimaha/restaurant-service-pyramid>`_

There are few things required to setup and run consumer tests.

Pact Helper
~~~~~~~~~~~

This helper class is used by Pact Test to start and stop the web-app before and after the test. It also defines the
ports and endpoint to be used by the test. The following is an example of Pact Helper:

.. code:: python

    class RestaurantPactHelper(PactHelper):
        process = None

        def setup(self):
            self.process = subprocess.Popen('gunicorn start:app -w 3 -b :8080 --log-level error', shell=True)

        def tear_down(self):
            self.process.kill()

There are few rules for the helper:

* it **must** extend :code:`PactHelper` class from :code:`pact_test`
* it **must** define a :code:`setup` method
* it **must** define a :code:`tear_down` method

It is also possible to override default url (*localhost*) and port (*9999*):

.. code:: python

    class RestaurantPactHelper(PactHelper):
        test_url = '0.0.0.0'
        test_port = 5000


States
~~~~~~

When a consumer sets a pact, it defines certain states. States are basically pre-requisites to your test. Before
honouring the pacts, a provider needs to define such states. For example:

.. code:: python

    @honours_pact_with('UberEats')
    @pact_uri('http://Kalimaha.github.io/src/pacts/pact.json')
    class UberEats(ServiceConsumerTest):

        @state('some menu items exist')
        def test_get_menu_items(self):
            DB.save(MenuItem('spam'))
            DB.save(MenuItem('eggs'))

In this example, the provider stores some test data in its DB in order to make the system ready to receive mock calls
from the consumer and therefore verify the pact.

Configuration
-------------

The default configuration of Pact Test assumes the following values:

* **consumer_tests_path:** :code:`tests/service_consumers`
* **provider_tests_path:** :code:`tests/service_providers`
* **pact_broker_uri:** :code:`None`

It is possible to override such values by creating a file named :code:`.pact.json` in the project's root. The following
is an example of a valid configuration file:

.. code:: json

  {
    "consumer_tests_path": "mypath/mytests",
    "provider_tests_path": "mypath/mytests",
    "pact_broker_uri": "http://example.com/"
  }

All fields are optional: only specified fields will override default configuration values.

Development
===========

Setup
~~~~~

.. code:: bash

  python3 setup.py install

Test
~~~~

It is possible to run the tests locally with Docker through the following command:

.. code:: bash

  $ ./bin/test

By default this command tests the library against Python 3.6. It is possible to specify the Python version as follows:

.. code:: bash

  $ ./bin/test <ENV>

Available values for `ENV` are: :code:`py27`, :code:`py33`, :code:`py34`, :code:`py35` :code:`py36`, :code:`py37` and
:code:`py38`. It is also possible to test all the versions at once with:

.. code:: bash

  $ ./bin/test all

Upload New Version

.. code:: bash

$ python3 setup.py sdist upload

With Python Wheels <http://pythonwheels.com/>_:

.. code:: bash

$ python3 setup.py sdist bdist_wheel $ twine upload dist/*