Create abstract fixture manager

Allow to decople global fixture definition from test
cases.

Fixtures can be defined as a subclass of tobiko.Fixture

  class MyFixture(tobiko.Fixture):
      ...

Tobiko will reference to it as: '<module-name>.MyFixture'
where module-name is the full name of the module where
the class is defined. Fixture name are accessible via
'fixture_name' class attribute.

tobiko.Fixture subclass has to implement bellow methods

  def create_fixture(self):
      # mandatory
      ...

  def delete_fixture(self):
      # optional method
      ...

Test cases to create a fixture should mane one of below
calls:

  fixture = tobiko.create_fixture(<fixture-name>)
  fixture = tobiko.create_fixture(<fixture-class>)

Existing fixtures can be find using one of below calls:

  fixture = tobiko.get_fixture(<fixture-name>)
  fixture = tobiko.get_fixture(<fixture-class>)

Existing fixtures can be deleted using one of below calls:

  tobiko.delete_fixture(<fixture-name>)
  tobiko.delete_fixture(<fixture-class>)

Change-Id: I5c104a732234ab2183fbfb9909cba4a445f59b60

tobiko/__init__.py

@@ -0,0 +1,22 @@
+#
+#    Licensed under the Apache License, Version 2.0 (the "License"); you may
+#    not use this file except in compliance with the License. You may obtain
+#    a copy of the License at
+#
+#         http://www.apache.org/licenses/LICENSE-2.0
+#
+#    Unless required by applicable law or agreed to in writing, software
+#    distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
+#    WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
+#    License for the specific language governing permissions and limitations
+#    under the License.
+from __future__ import absolute_import
+
+from tobiko.common.managers import fixture as fixture_manager
+
+
+Fixture = fixture_manager.Fixture
+
+get_fixture = fixture_manager.FIXTURES.get
+create_fixture = fixture_manager.FIXTURES.create
+delete_fixture = fixture_manager.FIXTURES.delete

tobiko/common/managers/fixture.py

@@ -0,0 +1,97 @@
+# Copyright 2018 Red Hat
+#
+#    Licensed under the Apache License, Version 2.0 (the "License"); you may
+#    not use this file except in compliance with the License. You may obtain
+#    a copy of the License at
+#
+#         http://www.apache.org/licenses/LICENSE-2.0
+#
+#    Unless required by applicable law or agreed to in writing, software
+#    distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
+#    WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
+#    License for the specific language governing permissions and limitations
+#    under the License.
+from __future__ import absolute_import
+
+
+import abc
+import inspect
+
+import six
+
+
+def get_fixture_name(obj):
+    if isinstance(obj, six.string_types):
+        return obj
+
+    elif (isinstance(obj, six.class_types) and
+          issubclass(obj, Fixture)):
+        return obj.fixture_name
+
+    msg = "{!r} is not a string type or a subclass of {!s}".format(
+        obj, Fixture)
+    raise TypeError(msg)
+
+
+class FixtureManager(object):
+
+    def __init__(self):
+        self.fixtures = {}
+
+    def set(self, name, cls):
+        if not issubclass(cls, Fixture):
+            msg = "{!r} is not a subclass of {!s}".format(cls, Fixture)
+            raise TypeError(msg)
+        fixture = cls()
+        actual_fixture = self.fixtures.setdefault(name, fixture)
+        if actual_fixture is not fixture:
+            msg = "Fixture with named {!r} already registered: {!r}".format(
+                name, actual_fixture)
+            raise ValueError(msg)
+        return fixture
+
+    def get(self, cls_or_name):
+        name = get_fixture_name(cls_or_name)
+        fixture = self.fixtures.get(name)
+        if fixture is None:
+            raise ValueError('Invalid fixture name: {!r}'.format(name))
+        return fixture
+
+    def create(self, cls_or_name):
+        fixture = self.get(cls_or_name)
+        fixture.create_fixture()
+        return fixture
+
+    def delete(self, cls_or_name):
+        fixture = self.get(cls_or_name)
+        fixture.delete_fixture()
+        return fixture
+
+
+FIXTURES = FixtureManager()
+
+
+class FixtureMeta(abc.ABCMeta):
+
+    def __new__(cls, name, bases, members):
+        fixture_class = super(FixtureMeta, cls).__new__(cls, name, bases,
+                                                        members)
+        if not inspect.isabstract(fixture_class):
+            fixture_name = getattr(fixture_class, 'fixture_name', None)
+            if fixture_name is None:
+                fixture_class.fixture_name = fixture_name = (
+                    fixture_class.__module__ + '.' +
+                    fixture_class.__name__)
+                FIXTURES.set(fixture_name, fixture_class)
+        return fixture_class
+
+
+@six.add_metaclass(FixtureMeta)
+class Fixture(object):
+
+    @abc.abstractmethod
+    def create_fixture(self):
+        pass
+
+    def delete_fixture(self):
+        pass

tobiko/tests/test_fixture.py

@@ -0,0 +1,89 @@
+# Copyright 2018 Red Hat
+#
+#    Licensed under the Apache License, Version 2.0 (the "License"); you may
+#    not use this file except in compliance with the License. You may obtain
+#    a copy of the License at
+#
+#         http://www.apache.org/licenses/LICENSE-2.0
+#
+#    Unless required by applicable law or agreed to in writing, software
+#    distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
+#    WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
+#    License for the specific language governing permissions and limitations
+#    under the License.
+from __future__ import absolute_import
+
+import tobiko
+from tobiko.tests import base
+
+
+class TestFixture(tobiko.Fixture):
+
+    def __init__(self):
+        self.created = False
+        self.deleted = False
+
+    reset = __init__
+
+    def create_fixture(self):
+        self.created = True
+
+    def delete_fixture(self):
+        self.deleted = True
+
+
+class FixtureTypeTest(base.TobikoTest):
+
+    fixture_type = TestFixture
+    fixture_name = __name__ + '.' + TestFixture.__name__
+
+    @classmethod
+    def setUpClass(cls):
+        super(FixtureTypeTest, cls).setUpClass()
+        cls.fixture = tobiko.get_fixture(cls.fixture_name)
+
+    def setUp(self):
+        super(FixtureTypeTest, self).setUp()
+        self.fixture.reset()
+
+    def test_fixture_type(self):
+        self.assertIsInstance(self.fixture, self.fixture_type)
+
+    def test_fixture_name(self):
+        self.assertEqual(self.fixture_name, self.fixture.fixture_name)
+
+    def test_get_fixture_by_name(self):
+        self._test_get_fixture(self.fixture_name)
+
+    def test_get_fixture_by_type(self):
+        self._test_get_fixture(self.fixture_type)
+
+    def _test_get_fixture(self, obj):
+        fixture = tobiko.get_fixture(obj)
+        self.assertIs(self.fixture, fixture)
+        self.assertFalse(fixture.created)
+        self.assertFalse(fixture.deleted)
+
+    def test_create_fixture_by_name(self):
+        self._test_create_fixture(self.fixture_name)
+
+    def test_create_fixture_by_type(self):
+        self._test_create_fixture(self.fixture_type)
+
+    def _test_create_fixture(self, obj):
+        fixture = tobiko.create_fixture(obj)
+        self.assertIs(self.fixture, fixture)
+        self.assertTrue(fixture.created)
+        self.assertFalse(fixture.deleted)
+
+    def test_delete_fixture_by_name(self):
+        self._test_delete_fixture(self.fixture_name)
+
+    def test_delete_fixture_by_type(self):
+        self._test_delete_fixture(self.fixture_type)
+
+    def _test_delete_fixture(self, obj=TestFixture):
+        fixture = tobiko.delete_fixture(obj)
+        self.assertIs(self.fixture, fixture)
+        self.assertFalse(fixture.created)
+        self.assertTrue(fixture.deleted)

tox.ini

@@ -1,5 +1,5 @@
 [tox]
-envlist = pep8,pylint,py35,py36,py27
+envlist = pep8,pylint,py35,py36,py37,py27
 
 minversion = 2.0
 
@@ -24,7 +24,7 @@ commands =
     find . -type f -name ".coverage*" -delete
     find . -type f -name "*.pyc" -delete
     coverage erase
-    stestr --test-path ./tobiko/tests/cmd run {posargs}
+    stestr --test-path ./tobiko/tests run --black-regex 'scenario' {posargs}
     coverage combine
     coverage html -d cover
     coverage xml -o cover/coverage.xml