Allow override_config for pytest (#338)

* provides: base override class; unittest and pytest overrides

* raise invalid config error earlier

* update AUTHORS

* avoid AttributeError

* fix comment

* add tests

* fix tests, update docstring

* update docs, improve tests

* fix docs

* fix markdown

* refactor pytest override, use hidden fixture, refactor base and unittest classes

* improve docstring and error

* refactor pytest override to use hooks

* set minimum pytest version

* revert empty lines removal

* introduce pytest test runner for package, refactoring

* WIP

* Finalize tox config, refactor docs, add global fixture

* skip py35

* pytest command: remove unnecessary ignore

* address comments

* Update constance/test/pytest.py

* address comments

* add test for checking nested markers

Co-authored-by: Camilo Nova <camilo.nova@gmail.com>
Co-authored-by: Paweł Zarębski <ppjzarebski@gmail.com>

.coveragerc

@@ -1,6 +1,8 @@
 [run]
 source = constance
 branch = 1
+omit =
+    */pytest.py
 
 [report]
-omit = *tests*,*migrations*
+omit = *tests*,*migrations*,.tox/*,setup.py,*settings.py

AUTHORS

@@ -40,6 +40,7 @@ saw2th <stephen@saw2th.co.uk>
 trbs <trbs@trbs.net>
 vl <1844144@gmail.com>
 vl <vl@u64.(none)>
+Vladas Tamoshaitis <amd.vladas@gmail.com>
 Dmitriy Tatarkin <mail@dtatarkin.ru>
 Alexandr Artemyev <mogost@gmail.com>
 Elisey Zanko <elisey.zanko@gmail.com>

constance/test/__init__.py

@@ -1 +1 @@
-from .utils import override_config
+from .unittest import override_config  # pragma: no cover

constance/test/pytest.py

@@ -0,0 +1,79 @@
+"""
+Pytest constance override config plugin.
+
+Inspired by https://github.com/pytest-dev/pytest-django/.
+"""
+import pytest
+from contextlib import ContextDecorator
+from constance import config as constance_config
+
+
+@pytest.hookimpl(trylast=True)
+def pytest_configure(config):  # pragma: no cover
+    """
+    Register override_config marker.
+    """
+    config.addinivalue_line(
+        "markers",
+        (
+            "override_config(**kwargs): "
+            "mark test to override django-constance config"
+        )
+    )
+
+
+@pytest.hookimpl(hookwrapper=True)
+def pytest_runtest_call(item):  # pragma: no cover
+    """
+    Validate constance override marker params. Run test with overrided config.
+    """
+    marker = item.get_closest_marker("override_config")
+    if marker is not None:
+        if marker.args:
+            pytest.fail(
+                "Constance override can not not accept positional args"
+            )
+        with override_config(**marker.kwargs):
+            yield
+    else:
+        yield
+
+
+class override_config(ContextDecorator):
+    """
+    Override config while running test function.
+
+    Act as context manager and decorator.
+    """
+    def enable(self):
+        """
+        Store original config values and set overridden values.
+        """
+        for key, value in self._to_override.items():
+            self._original_values[key] = getattr(constance_config, key)
+            setattr(constance_config, key, value)
+
+    def disable(self):
+        """
+        Set original values to the config.
+        """
+        for key, value in self._original_values.items():
+            setattr(constance_config, key, value)
+
+    def __init__(self, **kwargs):
+        self._to_override = kwargs.copy()
+        self._original_values = {}
+
+    def __enter__(self):
+        self.enable()
+
+    def __exit__(self, exc_type, exc_val, exc_tb):
+        self.disable()
+
+
+@pytest.fixture(name="override_config")
+def _override_config():
+    """
+    Make override_config available as a function fixture.
+    """
+    return override_config

docs/testing.rst

@@ -38,3 +38,73 @@ method level and also as a
         def test_what_is_your_favourite_color(self):
             with override_config(YOUR_FAVOURITE_COLOR="Blue?"):
                 self.assertEqual(config.YOUR_FAVOURITE_COLOR, "Blue?")
+
+
+Pytest usage
+~~~~~
+
+Django-constance provides pytest plugin that adds marker
+:class:`@pytest.mark.override_config()`. It handles config override for
+module/class/function, and automatically revert any changes made to the
+constance config values when test is completed.
+
+.. py:function:: pytest.mark.override_config(**kwargs)
+
+    Specify different config values for the marked tests in kwargs.
+
+Module scope override
+
+.. code-block:: python
+
+    pytestmark = pytest.mark.override_config(API_URL="/awesome/url/")
+
+    def test_api_url_is_awesome():
+        ...
+
+Class/function scope
+
+.. code-block:: python
+
+    from constance import config
+
+    @pytest.mark.override_config(API_URL="/awesome/url/")
+    class SomeClassTest:
+        def test_is_awesome_url(self):
+            assert config.API_URL == "/awesome/url/"
+
+        @pytest.mark.override_config(API_URL="/another/awesome/url/")
+        def test_another_awesome_url(self):
+            assert config.API_URL == "/another/awesome/url/"
+
+If you want to use override as a context manager or decorator, consider using
+
+.. code-block:: python
+
+    from constance.test.pytest import override_config
+
+    def test_override_context_manager():
+        with override_config(BOOL_VALUE=False):
+            ...
+    # or
+    @override_config(BOOL_VALUE=False)
+    def test_override_context_manager():
+        ...
+
+Pytest fixture as function or method parameter (
+NOTE: no import needed as fixture is available globally)
+
+.. code-block:: python
+
+    def test_api_url_is_awesome(override_config):
+        with override_config(API_URL="/awesome/url/"):
+            ...
+
+Any scope, auto-used fixture alternative can also be implemented like this
+
+.. code-block:: python
+
+    @pytest.fixture(scope='module', autouse=True)  # e.g. module scope
+    def api_url(override_config):
+        with override_config(API_URL="/awesome/url/"):
+            yield
+

setup.py

@@ -56,5 +56,10 @@ setup(
     extras_require={
         'database': ['django-picklefield'],
         'redis': ['redis'],
-    }
+    },
+    entry_points={
+        'pytest11': [
+            'pytest-django-constance = constance.test.pytest',
+        ],
+    },
 )

tests/test_pytest_overrides.py

@@ -0,0 +1,78 @@
+import unittest
+
+
+try:
+    import pytest
+
+    from constance import config
+    from constance.test.pytest import override_config
+
+
+    class TestPytestOverrideConfigFunctionDecorator:
+        """Test that the override_config decorator works correctly for Pytest classes.
+
+        Test usage of override_config on test method and as context manager.
+        """
+
+        def test_default_value_is_true(self):
+            """Assert that the default value of config.BOOL_VALUE is True."""
+            assert config.BOOL_VALUE
+
+        @pytest.mark.override_config(BOOL_VALUE=False)
+        def test_override_config_on_method_changes_config_value(self):
+            """Assert that the pytest mark decorator changes config.BOOL_VALUE."""
+            assert not config.BOOL_VALUE
+
+        def test_override_config_as_context_manager_changes_config_value(self):
+            """Assert that the context manager changes config.BOOL_VALUE."""
+            with override_config(BOOL_VALUE=False):
+                assert not config.BOOL_VALUE
+
+            assert config.BOOL_VALUE
+
+        @override_config(BOOL_VALUE=False)
+        def test_method_decorator(self):
+            """Ensure `override_config` can be used as test method decorator."""
+            assert not config.BOOL_VALUE
+
+
+    @pytest.mark.override_config(BOOL_VALUE=False)
+    class TestPytestOverrideConfigDecorator:
+        """Test that the override_config decorator works on classes."""
+
+        def test_override_config_on_class_changes_config_value(self):
+            """Asser that the class decorator changes config.BOOL_VALUE."""
+            assert not config.BOOL_VALUE
+
+        @pytest.mark.override_config(BOOL_VALUE='True')
+        def test_override_config_on_overrided_value(self):
+            """Ensure that method mark decorator changes already overrided value for class."""
+            assert config.BOOL_VALUE == 'True'
+
+
+    def test_fixture_override_config(override_config):
+        """
+        Ensure `override_config` fixture is available globally
+        and can be used in test functions.
+        """
+        with override_config(BOOL_VALUE=False):
+            assert not config.BOOL_VALUE
+
+    @override_config(BOOL_VALUE=False)
+    def test_func_decorator():
+        """Ensure `override_config` can be used as test function decorator."""
+        assert not config.BOOL_VALUE
+
+except ImportError:
+    pass
+
+
+class PytestTests(unittest.TestCase):
+    def setUp(self):
+        self.skipTest('Skip all pytest tests when using unittest')
+
+    def test_do_not_skip_silently(self):
+        """
+        If no at least one test present, unittest silently skips module.
+        """
+        pass

tox.ini

@@ -1,8 +1,8 @@
 [tox]
 envlist =
-    py{35,36,37,pypy3}-django{22}
-    py{36,37,38}-django{30}
-    py{36,37,38}-django-master
+    py{35,36,37,pypy3}-django{22}-unittest
+    py{36,37,38}-django{30,-master}-unittest
+    py{36,37,38,pypy3}-django{22,30,-master}-pytest
 
 [testenv]
 deps =
@@ -13,12 +13,16 @@ deps =
     django-22: Django>=2.2,<3.0
     django-30: Django>=3.0,<3.1
     django-master: https://github.com/django/django/archive/master.tar.gz
+    pytest: pytest
+    pytest: pytest-cov
+    pytest: pytest-django
 usedevelop = True
 ignore_outcome =
     django-master: True
 commands =
-    coverage run {envbindir}/django-admin test -v2
-    coverage report
+    unittest: coverage run {envbindir}/django-admin test -v2
+    unittest: coverage report
+    pytest: pytest --cov=. --ignore=.tox --disable-pytest-warnings {toxinidir}
 setenv =
     PYTHONDONTWRITEBYTECODE=1
     DJANGO_SETTINGS_MODULE=tests.settings