Add tests and docs for config classes

This commit adds a few basic tests to check things work as expected.

README.rst

@@ -44,31 +44,34 @@ Add ``'adyen'`` to ``INSTALLED_APPS`` and run::
 to create the appropriate database tables.
 
 Configuration
--------------
+=============
 
-Edit your ``settings.py`` to set the following settings:
-
-.. code-block:: python
+You have two approaches to configure `django-oscar-adyen`.
 
-    ADYEN_IDENTIFIER = 'YourAdyenAccountName'
-    ADYEN_SECRET_KEY = 'YourAdyenSkinSecretKey'
-    ADYEN_ACTION_URL = 'https://test.adyen.com/hpp/select.shtml'
+Settings-based configuration
+----------------------------
+For simple deployments, setting the required values in the settings will suffice.
 
-Obviously, you'll need to specify different settings in your test environment
-as opposed to your production environment.
+Edit your ``settings.py`` to set the following settings:
 
+* ``ADYEN_IDENTIFIER`` - The identifier of your Adyen account.
+* ``ADYEN_SKIN_CODE`` -  The code for your Adyen skin.
+* ``ADYEN_SECRET_KEY`` - The secret key defined in your Adyen skin.
+* ``ADYEN_ACTION_URL`` -
+  The URL towards which the Adyen form should be POSTed to initiate the payment process
+  (e.g. 'https://test.adyen.com/hpp/select.shtml').
+* ``ADYEN_IP_ADDRESS_HTTP_HEADER`` - Optional. The header in `META` to inspect to determine
+  the IP address of the request. Defaults to `REMOTE_ADDR`.
 
-Settings
-========
+You will likely need to specify different settings in your test environment
+as opposed to your production environment.
 
-====================== =========================================================
- Setting                Description
----------------------- ---------------------------------------------------------
- ``ADYEN_IDENTIFIER``   The identifier of your Adyen account
- ``ADYEN_SECRET_KEY``   The secret key defined in your Adyen skin
- ``ADYEN_ACTION_URL``   The URL towards which the Adyen form should be POSTed
-                        to initiate the payment process
-====================== =========================================================
+Class-based configuration
+-------------------------
+In more complex deployments, you will want to e.g. alter the Adyen identifier based on
+the request. That is not easily implemented with Django settings, so you can alternatively
+set ``ADYEN_CONFIG_CLASS`` to a config class of your own.
+See `adyen.settings_config.FromSettingsConfig` for an example.
 
 License
 =======

tests/test_adyen.py

@@ -4,8 +4,6 @@
 import six
 from unittest.mock import Mock
 
-from django.conf import settings
-from django.core.exceptions import ImproperlyConfigured
 from django.test import TestCase
 from django.test.utils import override_settings
 
@@ -140,11 +138,6 @@ def test_form_action(self):
         action_url = self.scaffold.get_form_action()
         self.assertEqual(action_url, TEST_ACTION_URL)
 
-        # If the setting is missing, a proper exception is raised
-        del settings.ADYEN_ACTION_URL
-        with self.assertRaises(ImproperlyConfigured):
-            self.scaffold.get_form_action()
-
     def test_form_fields_ok(self):
         """
         Test that the payment form fields are properly built.

tests/test_config.py

@@ -0,0 +1,61 @@
+from django.conf import settings
+from django.core.exceptions import ImproperlyConfigured
+
+from django.test import TestCase
+from django.test.utils import override_settings
+
+from adyen.config import get_config
+
+
+@override_settings(
+    ADYEN_IDENTIFIER='foo',
+    ADYEN_SECRET_KEY='foo',
+    ADYEN_ACTION_URL='foo',
+    ADYEN_SKIN_CODE='foo',
+)
+class FromSettingsTestCase(TestCase):
+    """
+    This test case tests the FromSettings confic class, which just fetches its
+    values from the Django settings.
+    """
+
+    def test_is_default(self):
+        assert 'FromSettingsConfig' in get_config().__class__.__name__
+
+    def test_value_passing_works(self):
+        assert get_config().get_action_url() == 'foo'
+
+    # https://docs.djangoproject.com/en/1.8/topics/testing/tools/#django.test.modify_settings
+    # Override settings is needed to let us delete settings on a per-test basis.
+    @override_settings()
+    def test_complains_when_not_fully_configured(self):
+        # If the setting is missing, a proper exception is raised
+        del settings.ADYEN_ACTION_URL
+        with self.assertRaises(ImproperlyConfigured):
+            get_config()
+
+
+class DummyConfigClass:
+
+    def get_action_url(self):
+        return 'foo'
+
+
+@override_settings(ADYEN_CONFIG_CLASS='tests.test_config.DummyConfigClass')
+class CustomConfigClassTestCase(TestCase):
+    """
+    This test case checks that it's possible to replace the FromSettings confic class
+    by one's own, and that it is used to fetch values as expected.
+    """
+
+    def test_class_gets_picked_up(self):
+        assert 'DummyConfigClass' in get_config().__class__.__name__
+
+    @override_settings(ADYEN_ACTION_URL='bar')
+    def test_settings_ignored(self):
+        """
+        Check that we indeed ignore Django settings (apart from the config class).
+        """
+        assert get_config().get_action_url() == 'foo'
+
+