Change how required settings are handled

Certain settings are going to be required for the application to run.
Currently `SECRET_KEY` is the only one, but the list will most likely
grow over time. The application factory allows for the settings in
`settings.py` to be overridden a couple of different ways. Required
settings should be checked after all of the overrides have been
processed.

This is being implemented in the form of a helper function that checks
for the required keys. Because `settings.py` will add the key to the
configuration, `DOES_NOT_EXIST` is a value that can be assigned to a key
that is intended to be required. `check_required_settings` will respect
both the absence of the key and the value `DOES_NOT_EXIST`.

Along with this change comes some tests. These two tests are the
groundwork for the eventual suite of tests. `tox` can be used to run the
tests. `tox` requires a `setup.py` in order to install the package into
the virtualenv, so a minimal one is being added for that purpose.

Fixes #32

.coveragerc

@@ -0,0 +1,6 @@
+[run]
+branch = True
+
+[report]
+exclude_lines =
+    if __name__ == '__main__:

.gitignore

@@ -1,3 +1,5 @@
+# Local/private stuffs
+instance
 settings.cfg
 
 # Frontend preprocessors

README.rst

@@ -96,6 +96,20 @@ A list of issues can be found on GitHub_. Issues are categorized as graphics
 
 Pick one and start hacking away!
 
+Testing
+-------
+
+Before you push your changes back to GitHub and submit a pull request, you
+probably want to run the test suite. To prepare for running the tests, install
+the testing requirements::
+
+    $ pip install -r tests/requirements.txt
+
+The test suite can be run with tox_::
+
+    $ tox
+
 After you're done, be sure to add your name and GitHub profile to AUTHORS.rst.
 
 .. _GitHub: https://github.com/NYCPython/nycpython.com/issues
+.. _tox: http://tox.rtfd.org

nycpython/factory.py

@@ -2,7 +2,7 @@
 
 from flask import Flask
 
-from nycpython.utils import register_blueprints
+from nycpython.utils import check_required_settings, register_blueprints
 
 __all__ = 'create_app',
 
@@ -25,6 +25,8 @@ def create_app(package_name, package_path, settings_override=None,
     app.config.from_pyfile('settings.cfg', silent=True)
     app.config.from_object(settings_override)
 
+    check_required_settings(app.config)
+
     register_blueprints(app, package_name, package_path)
 
     return app

nycpython/settings.py

@@ -2,26 +2,19 @@
 
 from os import environ as env
 
+from nycpython.utils import DOES_NOT_EXIST
+
 
 def bool_(key, default):
     """Return an environment setting represented as a boolean."""
     return env.get(key, str(default)).lower() == 'true'
 
 
-def required(key):
-    """Return the value for a required environment setting."""
-    try:
-        return env[key]
-    except KeyError:
-        message = 'The {} environment setting is required.'.format(key)
-        raise RuntimeError(message)
-
-
 DEBUG = bool_('DEBUG', False)
-SECRET_KEY = required('SECRET_KEY')
+SECRET_KEY = env.get('SECRET_KEY', DOES_NOT_EXIST)
 
 # Flask-Assets
-ASSESTS_BUDEG = bool_('ASSETS_DEBUG', False)
+ASSESTS_DEBUG = bool_('ASSETS_DEBUG', False)
 
 # Flask-Cache
 CACHE_REDIS_URL = env.get('CACHE_REDIS_URL')
@@ -33,4 +26,4 @@ def required(key):
 
 del bool_
 del env
-del required
+del DOES_NOT_EXIST

nycpython/utils.py

@@ -5,7 +5,17 @@
 
 from flask import Blueprint
 
-__all__ = 'register_blueprints',
+__all__ = 'check_required_settings', 'register_blueprints',
+
+DOES_NOT_EXIST = '!@DNE@!'  # Placeholder value to use for missing settings.
+
+
+def check_required_settings(config, keys=('SECRET_KEY',)):
+    """Validate the presence of required settings."""
+    for key in keys:
+        if config.get(key, DOES_NOT_EXIST) == DOES_NOT_EXIST:
+            message = 'The {} configuration settings is required.'.format(key)
+            raise RuntimeError(message)
 
 
 def register_blueprints(app, package_name, package_path):

setup.py

@@ -0,0 +1,3 @@
+from setuptools import setup
+
+setup(name='nycpython', version='1.0.0')

tests/requirements.txt

@@ -0,0 +1 @@
+tox

tests/test_utils.py

@@ -0,0 +1,21 @@
+import pytest
+
+from nycpython import utils
+
+
+@pytest.fixture(scope='module')
+def config():
+    return {
+        'KEY1': 1,
+        'KEY2': 2,
+    }
+
+
+def test_check_required_settings(config):
+    assert utils.check_required_settings(config, ('KEY1', 'KEY2')) is None
+
+
+def test_check_required_settings_missing_key(config):
+    with pytest.raises(RuntimeError) as e:
+        utils.check_required_settings(config, ('KEY1', 'KEY3'))
+    assert 'KEY3' in e.value.args[0]

tox.ini

@@ -0,0 +1,11 @@
+[tox]
+envlist = py33
+
+[testenv]
+deps =
+    coverage
+    factory_boy
+    pytest
+commands =
+    coverage run --source nycpython -m pytest tests
+    coverage report -m