===================
Testing in Graphene
===================


Automated testing is an extremely useful bug-killing tool for the modern developer. You can use a collection of tests – a test suite – to solve, or avoid, a number of problems:

- When you’re writing new code, you can use tests to validate your code works as expected.
- When you’re refactoring or modifying old code, you can use tests to ensure your changes haven’t affected your application’s behavior unexpectedly.

Testing a GraphQL application is a complex task, because a GraphQL application is made of several layers of logic – schema definition, schema validation, permissions and field resolution.

With Graphene test-execution framework and assorted utilities, you can simulate GraphQL requests, execute mutations, inspect your application’s output and generally verify your code is doing what it should be doing.


Testing tools
-------------

Graphene provides a small set of tools that come in handy when writing tests.


Test Client
~~~~~~~~~~~

The test client is a Python class that acts as a dummy GraphQL client, allowing you to test your views and interact with your Graphene-powered application programmatically.

Some of the things you can do with the test client are:

- Simulate Queries and Mutations and observe the response.
- Test that a given query request is rendered by a given Django template, with a template context that contains certain values.


Overview and a quick example
~~~~~~~~~~~~~~~~~~~~~~~~~~~~

To use the test client, instantiate ``graphene.test.Client`` and retrieve GraphQL responses:


.. code:: python

    from graphene.test import Client

    def test_hey():
        client = Client(my_schema)
        executed = client.execute('''{ hey }''')
        assert executed == {
            'data': {
                'hey': 'hello!'
            }
        }


Execute parameters
~~~~~~~~~~~~~~~~~~

You can also add extra keyword arguments to the ``execute`` method, such as
``context``, ``root``, ``variables``, ...:


.. code:: python

    from graphene.test import Client

    def test_hey():
        client = Client(my_schema)
        executed = client.execute('''{ hey }''', context={'user': 'Peter'})
        assert executed == {
            'data': {
                'hey': 'hello Peter!'
            }
        }