Add catalog subsets

dependency_injector/__init__.py

@@ -1,6 +1,7 @@
 """Dependency injector."""
 
 from .catalog import AbstractCatalog
+from .catalog import CatalogSubset
 from .catalog import override
 
 from .providers import Provider
@@ -30,6 +31,7 @@ from .utils import is_kwarg_injection
 from .utils import is_attribute_injection
 from .utils import is_method_injection
 from .utils import is_catalog
+from .utils import is_catalog_subset
 
 from .errors import Error
 
@@ -37,6 +39,7 @@ from .errors import Error
 __all__ = (
     # Catalogs
     'AbstractCatalog',
+    'CatalogSubset',
     'override',
 
     # Providers
@@ -69,6 +72,7 @@ __all__ = (
     'is_attribute_injection',
     'is_method_injection',
     'is_catalog',
+    'is_catalog_subset',
 
     # Errors
     'Error',

dependency_injector/catalog.py

@@ -31,6 +31,10 @@ class CatalogMetaClass(type):
         attributes['providers'] = providers
         return type.__new__(mcs, class_name, bases, attributes)
 
+    def __repr__(cls):
+        """Return string representation of the catalog class."""
+        return '<Catalog "' + '.'.join((cls.__module__, cls.__name__)) + '">'
+
 
 @six.add_metaclass(CatalogMetaClass)
 class AbstractCatalog(object):
@@ -53,22 +57,20 @@ class AbstractCatalog(object):
     inherited_providers = dict()
 
     __IS_CATALOG__ = True
-    __slots__ = ('used_providers',)
 
-    def __init__(self, *used_providers):
+    def __new__(cls, *providers):
-        """Initializer."""
+        """Catalog constructor.
-        self.used_providers = set(used_providers)
 
-    def __getattribute__(self, item):
+        Catalogs are declaratives entities that could not be instantiated.
-        """Return providers."""
+        Catalog constructor is designed to produce subsets of catalog
-        attribute = super(AbstractCatalog, self).__getattribute__(item)
+        providers.
-        if item in ('providers', 'used_providers', '__class__'):
+        """
-            return attribute
+        return CatalogSubset(catalog=cls, providers=providers)
 
-        if attribute not in self.used_providers:
+    @classmethod
-            raise Error('Provider \'{0}\' '.format(item) +
+    def is_subset_owner(cls, subset):
-                        'is not listed in dependencies')
+        """Check if catalog is subset owner."""
-        return attribute
+        return subset.catalog is cls
 
     @classmethod
     def filter(cls, provider_type):
@@ -86,6 +88,68 @@ class AbstractCatalog(object):
         for name, provider in six.iteritems(overriding.cls_providers):
             cls.providers[name].override(provider)
 
+    @classmethod
+    def get(cls, name):
+        """Return provider with specified name or raises error."""
+        try:
+            return cls.providers[name]
+        except KeyError:
+            raise Error('{0} has no provider with such name - {1}'.format(
+                cls, name))
+
+    @classmethod
+    def has(cls, name):
+        """Check if there is provider with certain name."""
+        return name in cls.providers
+
+
+class CatalogSubset(object):
+    """Subset of catalog providers."""
+
+    __IS_SUBSET__ = True
+    __slots__ = ('catalog', 'available_providers', 'providers', '__dict__')
+
+    def __init__(self, catalog, providers):
+        """Initializer."""
+        self.catalog = catalog
+        self.available_providers = set(providers)
+        self.providers = dict()
+        for provider_name in self.available_providers:
+            try:
+                provider = self.catalog.providers[provider_name]
+            except KeyError:
+                raise Error('Subset could not add "{0}" provider in scope, '
+                            'because {1} has no provider with '
+                            'such name'.format(provider_name, self.catalog))
+            else:
+                self.providers[provider_name] = provider
+        self.__dict__.update(self.providers)
+        super(CatalogSubset, self).__init__()
+
+    def get(self, name):
+        """Return provider with specified name or raises error."""
+        try:
+            return self.providers[name]
+        except KeyError:
+            self._raise_undefined_provider_error(name)
+
+    def has(self, name):
+        """Check if there is provider with certain name."""
+        return name in self.providers
+
+    def __getattr__(self, item):
+        """Raise an error on every attempt to get undefined provider."""
+        self._raise_undefined_provider_error(item)
+
+    def __repr__(self):
+        """Return string representation of subset."""
+        return '<Subset ({0}), {1}>'.format(
+            ', '.join(self.available_providers), self.catalog)
+
+    def _raise_undefined_provider_error(self, name):
+        """Raise error for cases when there is no such provider in subset."""
+        raise Error('Provider "{0}" is not a part of {1}'.format(name, self))
+
 
 def override(catalog):
     """Catalog overriding decorator."""

dependency_injector/utils.py

@@ -62,6 +62,12 @@ def is_catalog(instance):
             getattr(instance, '__IS_CATALOG__', False) is True)
 
 
+def is_catalog_subset(instance):
+    """Check if instance is catalog subset instance."""
+    return (not isinstance(instance, six.class_types) and
+            getattr(instance, '__IS_SUBSET__', False) is True)
+
+
 def get_injectable_kwargs(kwargs, injections):
     """Return dictionary of kwargs, patched with injections."""
     init_kwargs = dict(((injection.name, injection.value)

docs/catalogs/index.rst

@@ -16,76 +16,10 @@ Also, for both of these and some other cases, it might be useful to attach
 some init / shutdown functionality or something else, that deals with group 
 of providers.
 
-Writing catalogs
+..  toctree::
-----------------
+    :maxdepth: 2
 
-Catalogs have to extend base catalog class ``di.AbstractCatalog``.
+    writing
-
+    operating
-Providers have to be defined like catalog's attributes. Every provider in
+    subsets
-catalog has name. This name should follow ``some_provider`` convention, 
+    overriding
-that is standard naming convention for attribute names in Python.
-
-.. note::
-
-    It might be useful to add such ``""":type: (di.Provider) -> Object1"""`` 
-    documentation blocks one line after provider definition for every provider.
-    It will help code analyzing tools and IDE's to understand that variable 
-    above contains some callable object, that returns particular instance 
-    in a result of call.
-
-Example:
-
-.. image:: /images/catalogs/simple.png
-    :width: 100%
-    :align: center
-
-.. literalinclude:: ../../examples/catalogs/simple.py
-   :language: python
-
-Operating with catalog providers
---------------------------------
-
-``di.AbstractCatalog`` has several features that could be useful for some kind 
-of operations on catalog's providers:
-
-- ``di.AbstractCatalog.providers`` is read-only attribute that contains 
-  ``dict`` of all catalog providers, including providers that are inherited 
-  from parent catalogs, where key is the name of provider and value is 
-  provider itself.
-- ``di.AbstractCatalog.cls_providers`` is read-only attribute contains ``dict``
-  of current catalog providers, where key is the name of provider and value is 
-  provider itself.
-- ``di.AbstractCatalog.inherited_providers`` is read-only attribute contains 
-  ``dict`` of all providers that are inherited from parent catalogs, where key 
-  is the name of provider and value is provider itself. 
-- ``di.AbstractCatalog.filter(provider_type=di.Provider)`` is a class method 
-  that could be used for filtering catalog providers by provider types 
-  (for example, for getting all ``di.Factory`` providers). 
-  ``di.AbstractCatalog.filter()`` method use ``di.AbstractCatalog.providers``.
-
-Example:
-
-.. literalinclude:: ../../examples/catalogs/operating_with_providers.py
-   :language: python
-
-Overriding of catalogs
-----------------------
-
-Catalogs can be overridden by other catalogs. This, actually, means that 
-all of the providers from overriding catalog will override providers with the 
-same names in overridden catalog.
-
-There are two ways to override catalog by another catalog:
-
-- Use ``di.AbstractCatalog.override(AnotherCatalog)`` method.
-- Use ``@di.override(AnotherCatalog)`` class decorator.
-
-Example of overriding catalog using ``di.AbstractCatalog.override()`` method:
-
-.. literalinclude:: ../../examples/catalogs/override.py
-   :language: python
-
-Example of overriding catalog using ``@di.override()`` decorator:
-
-.. literalinclude:: ../../examples/catalogs/override_decorator.py
-   :language: python

docs/catalogs/operating.rst

@@ -0,0 +1,29 @@
+Operating with catalogs
+-----------------------
+
+``di.AbstractCatalog`` has several features that could be useful for some kind 
+of operations on catalog's providers:
+
+- ``di.AbstractCatalog.providers`` is read-only attribute that contains 
+  ``dict`` of all catalog providers, including providers that are inherited 
+  from parent catalogs, where key is the name of provider and value is 
+  provider itself.
+- ``di.AbstractCatalog.cls_providers`` is read-only attribute contains ``dict``
+  of current catalog providers, where key is the name of provider and value is 
+  provider itself.
+- ``di.AbstractCatalog.inherited_providers`` is read-only attribute contains 
+  ``dict`` of all providers that are inherited from parent catalogs, where key 
+  is the name of provider and value is provider itself. 
+- ``di.AbstractCatalog.filter(provider_type=di.Provider)`` is a class method 
+  that could be used for filtering catalog providers by provider types 
+  (for example, for getting all ``di.Factory`` providers). 
+  ``di.AbstractCatalog.filter()`` method use ``di.AbstractCatalog.providers``.
+
+Example:
+
+.. image:: /images/catalogs/operating_with_providers.png
+    :width: 100%
+    :align: center
+
+.. literalinclude:: ../../examples/catalogs/operating_with_providers.py
+   :language: python

docs/catalogs/overriding.rst

@@ -0,0 +1,22 @@
+Overriding of catalogs
+----------------------
+
+Catalogs can be overridden by other catalogs. This, actually, means that 
+all of the providers from overriding catalog will override providers with the 
+same names in overridden catalog.
+
+There are two ways to override catalog by another catalog:
+
+- Use ``di.AbstractCatalog.override(AnotherCatalog)`` method.
+- Use ``@di.override(AnotherCatalog)`` class decorator.
+
+Example of overriding catalog using ``di.AbstractCatalog.override()`` method:
+
+.. literalinclude:: ../../examples/catalogs/override.py
+   :language: python
+
+Example of overriding catalog using ``@di.override()`` decorator:
+
+.. literalinclude:: ../../examples/catalogs/override_decorator.py
+   :language: python
+

docs/catalogs/subsets.rst

@@ -0,0 +1,19 @@
+Creating catalog subsets
+------------------------
+
+``di.AbstractCatalog`` subset is a limited collection of catalog providers. 
+While catalog could be used as a centralized place for particular providers 
+group, such subsets of catalog providers can be used for creating several 
+limited scopes that could be passed to different subsystems.
+
+``di.AbstractCatalog`` subsets could be created by instantiating of particular 
+catalog with passing provider names to the constructor.
+
+Example:
+
+.. image:: /images/catalogs/subsets.png
+    :width: 100%
+    :align: center
+
+.. literalinclude:: ../../examples/catalogs/subsets.py
+   :language: python

docs/catalogs/writing.rst

@@ -0,0 +1,25 @@
+Writing catalogs
+----------------
+
+Catalogs have to extend base catalog class ``di.AbstractCatalog``.
+
+Providers have to be defined like catalog's attributes. Every provider in
+catalog has name. This name should follow ``some_provider`` convention, 
+that is standard naming convention for attribute names in Python.
+
+.. note::
+
+    It might be useful to add such ``""":type: (di.Provider) -> Object1"""`` 
+    docstrings just on the next line after provider's definition.  It will 
+    help code analyzing tools and IDE's to understand that variable above 
+    contains some callable object, that returns particular instance as a 
+    result of its call.
+
+Here is an simple example of catalog with several factories:
+
+.. image:: /images/catalogs/writing_catalogs.png
+    :width: 85%
+    :align: center
+
+.. literalinclude:: ../../examples/catalogs/writing_catalogs.py
+   :language: python

docs/main/changelog.rst

@@ -12,7 +12,10 @@ Development version
 -------------------
 
 - Add functionality for decorating classes with ``@di.inject``.
+- Add functionality for creating ``di.AbstractCatalog`` subsets.
 - Add enhancement for ``di.AbstractCatalog`` inheritance.
+- Add images for catalog "Writing catalogs" and "Operating with catalogs" 
+  examples.
 - Add minor refactorings and code style fixes.
 
 0.9.5

examples/catalogs/simple.py

@@ -1,37 +0,0 @@
-"""Catalog example."""
-
-import collections
-import dependency_injector as di
-
-
-# Creating some example classes:
-Object1 = collections.namedtuple('Object1', ['arg1', 'arg2'])
-Object2 = collections.namedtuple('Object2', ['object1'])
-
-
-class Catalog(di.AbstractCatalog):
-    """Providers catalog."""
-
-    object1_factory = di.Factory(Object1,
-                                 arg1=1,
-                                 arg2=2)
-    """:type: (di.Provider) -> Object1"""
-
-    object2_factory = di.Factory(Object2,
-                                 object1=object1_factory)
-    """:type: (di.Provider) -> Object2"""
-
-# Creating some objects:
-object2_1 = Catalog.object2_factory()
-object2_2 = Catalog.object2_factory()
-
-# Making some asserts:
-assert object2_1 is not object2_2
-
-assert isinstance(object2_1, Object2)
-assert object2_1.object1.arg1 == 1
-assert object2_1.object1.arg2 == 2
-
-assert isinstance(object2_2, Object2)
-assert object2_2.object1.arg1 == 1
-assert object2_2.object1.arg2 == 2

examples/catalogs/subsets.py

@@ -0,0 +1,59 @@
+"""Catalog subsets example."""
+
+import dependency_injector as di
+
+
+# Declaring example services catalog:
+class Services(di.AbstractCatalog):
+    """Example catalog of service providers."""
+
+    users = di.Provider()
+
+    auth = di.Provider()
+
+    photos = di.Provider()
+
+
+# Declaring example base class for some web views:
+class BaseWebView(object):
+    """Example base class of web view."""
+
+    def __init__(self, services):
+        """Initializer.
+
+        :type services: Services
+        :param services: Subset of service providers
+        """
+        self.services = services
+
+
+# Declaring several example web views:
+class AuthView(BaseWebView):
+    """Example auth web view."""
+
+
+class PhotosView(BaseWebView):
+    """Example photo processing web view."""
+
+# Creating example views with appropriate service provider subsets:
+auth_view = AuthView(Services('users', 'auth'))
+photos_view = PhotosView(Services('users', 'photos'))
+
+# Making some asserts:
+assert auth_view.services.users is Services.users
+assert auth_view.services.auth is Services.auth
+try:
+    auth_view.services.photos
+except di.Error:
+    # `photos` service provider is not in scope of `auth_view` services subset,
+    # so `di.Error` will be raised.
+    pass
+
+assert photos_view.services.users is Services.users
+assert photos_view.services.photos is Services.photos
+try:
+    photos_view.services.auth
+except di.Error as exception:
+    # `auth` service provider is not in scope of `photo_processing_view`
+    # services subset, so `di.Error` will be raised.
+    pass

examples/catalogs/writing_catalogs.py

@@ -0,0 +1,22 @@
+"""Catalog example."""
+
+import dependency_injector as di
+
+
+class Catalog(di.AbstractCatalog):
+    """Providers catalog."""
+
+    factory1 = di.Factory(object)
+    """:type: (di.Provider) -> object"""
+
+    factory2 = di.Factory(object)
+    """:type: (di.Provider) -> object"""
+
+# Creating some objects:
+object1 = Catalog.factory1()
+object2 = Catalog.factory2()
+
+# Making some asserts:
+assert object1 is not object2
+assert isinstance(object1, object)
+assert isinstance(object2, object)

tests/test_catalog.py

@@ -4,93 +4,159 @@ import unittest2 as unittest
 import dependency_injector as di
 
 
-class CatalogsInheritanceTests(unittest.TestCase):
-    """Catalogs inheritance tests."""
-
 class CatalogA(di.AbstractCatalog):
     """Test catalog A."""
 
     p11 = di.Provider()
     p12 = di.Provider()
 
+
 class CatalogB(CatalogA):
     """Test catalog B."""
 
     p21 = di.Provider()
     p22 = di.Provider()
 
+
 class CatalogC(CatalogB):
     """Test catalog C."""
 
     p31 = di.Provider()
     p32 = di.Provider()
 
+
+class CatalogsInheritanceTests(unittest.TestCase):
+    """Catalogs inheritance tests."""
+
     def test_cls_providers(self):
         """Test `di.AbstractCatalog.cls_providers` contents."""
-        self.assertDictEqual(self.CatalogA.cls_providers,
+        self.assertDictEqual(CatalogA.cls_providers,
-                             dict(p11=self.CatalogA.p11,
+                             dict(p11=CatalogA.p11,
-                                  p12=self.CatalogA.p12))
+                                  p12=CatalogA.p12))
-        self.assertDictEqual(self.CatalogB.cls_providers,
+        self.assertDictEqual(CatalogB.cls_providers,
-                             dict(p21=self.CatalogB.p21,
+                             dict(p21=CatalogB.p21,
-                                  p22=self.CatalogB.p22))
+                                  p22=CatalogB.p22))
-        self.assertDictEqual(self.CatalogC.cls_providers,
+        self.assertDictEqual(CatalogC.cls_providers,
-                             dict(p31=self.CatalogC.p31,
+                             dict(p31=CatalogC.p31,
-                                  p32=self.CatalogC.p32))
+                                  p32=CatalogC.p32))
 
     def test_inherited_providers(self):
         """Test `di.AbstractCatalog.inherited_providers` contents."""
-        self.assertDictEqual(self.CatalogA.inherited_providers, dict())
+        self.assertDictEqual(CatalogA.inherited_providers, dict())
-        self.assertDictEqual(self.CatalogB.inherited_providers,
+        self.assertDictEqual(CatalogB.inherited_providers,
-                             dict(p11=self.CatalogA.p11,
+                             dict(p11=CatalogA.p11,
-                                  p12=self.CatalogA.p12))
+                                  p12=CatalogA.p12))
-        self.assertDictEqual(self.CatalogC.inherited_providers,
+        self.assertDictEqual(CatalogC.inherited_providers,
-                             dict(p11=self.CatalogA.p11,
+                             dict(p11=CatalogA.p11,
-                                  p12=self.CatalogA.p12,
+                                  p12=CatalogA.p12,
-                                  p21=self.CatalogB.p21,
+                                  p21=CatalogB.p21,
-                                  p22=self.CatalogB.p22))
+                                  p22=CatalogB.p22))
 
     def test_providers(self):
         """Test `di.AbstractCatalog.inherited_providers` contents."""
-        self.assertDictEqual(self.CatalogA.providers,
+        self.assertDictEqual(CatalogA.providers,
-                             dict(p11=self.CatalogA.p11,
+                             dict(p11=CatalogA.p11,
-                                  p12=self.CatalogA.p12))
+                                  p12=CatalogA.p12))
-        self.assertDictEqual(self.CatalogB.providers,
+        self.assertDictEqual(CatalogB.providers,
-                             dict(p11=self.CatalogA.p11,
+                             dict(p11=CatalogA.p11,
-                                  p12=self.CatalogA.p12,
+                                  p12=CatalogA.p12,
-                                  p21=self.CatalogB.p21,
+                                  p21=CatalogB.p21,
-                                  p22=self.CatalogB.p22))
+                                  p22=CatalogB.p22))
-        self.assertDictEqual(self.CatalogC.providers,
+        self.assertDictEqual(CatalogC.providers,
-                             dict(p11=self.CatalogA.p11,
+                             dict(p11=CatalogA.p11,
-                                  p12=self.CatalogA.p12,
+                                  p12=CatalogA.p12,
-                                  p21=self.CatalogB.p21,
+                                  p21=CatalogB.p21,
-                                  p22=self.CatalogB.p22,
+                                  p22=CatalogB.p22,
-                                  p31=self.CatalogC.p31,
+                                  p31=CatalogC.p31,
-                                  p32=self.CatalogC.p32))
+                                  p32=CatalogC.p32))
+
+
+class CatalogSubsetTests(unittest.TestCase):
+    """Catalog subset test cases."""
+
+    catalog = None
+
+    def setUp(self):
+        """Set test environment up."""
+        self.subset = CatalogC('p11', 'p12')
+
+    def test_get_attr_from_subset(self):
+        """Test get providers (attribute) from subset."""
+        self.assertIs(self.subset.p11, CatalogC.p11)
+        self.assertIs(self.subset.p12, CatalogC.p12)
+
+    def test_get_attr_not_from_subset(self):
+        """Test get providers (attribute) that are not in subset."""
+        self.assertRaises(di.Error, getattr, self.subset, 'p21')
+        self.assertRaises(di.Error, getattr, self.subset, 'p22')
+        self.assertRaises(di.Error, getattr, self.subset, 'p31')
+        self.assertRaises(di.Error, getattr, self.subset, 'p32')
+
+    def test_get_method_from_subset(self):
+        """Test get providers (get() method) from subset."""
+        self.assertIs(self.subset.get('p11'), CatalogC.p11)
+        self.assertIs(self.subset.get('p12'), CatalogC.p12)
+
+    def test_get_method_not_from_subset(self):
+        """Test get providers (get() method) that are not in subset."""
+        self.assertRaises(di.Error, self.subset.get, 'p21')
+        self.assertRaises(di.Error, self.subset.get, 'p22')
+        self.assertRaises(di.Error, self.subset.get, 'p31')
+        self.assertRaises(di.Error, self.subset.get, 'p32')
+
+    def test_has(self):
+        """Test checks of providers availability in subsets."""
+        self.assertTrue(self.subset.has('p11'))
+        self.assertTrue(self.subset.has('p12'))
+
+        self.assertFalse(self.subset.has('p21'))
+        self.assertFalse(self.subset.has('p22'))
+        self.assertFalse(self.subset.has('p31'))
+        self.assertFalse(self.subset.has('p32'))
+
+    def test_creating_with_undefined_provider(self):
+        """Test subset creation with provider that is not in catalog."""
+        self.assertRaises(di.Error, CatalogC, 'undefined_provider')
 
 
 class CatalogTests(unittest.TestCase):
     """Catalog test cases."""
 
-    class Catalog(di.AbstractCatalog):
+    def test_get(self):
-        """Test catalog."""
+        """Test getting of providers using get() method."""
+        self.assertIs(CatalogC.get('p11'), CatalogC.p11)
+        self.assertIs(CatalogC.get('p12'), CatalogC.p12)
+        self.assertIs(CatalogC.get('p22'), CatalogC.p22)
+        self.assertIs(CatalogC.get('p22'), CatalogC.p22)
+        self.assertIs(CatalogC.get('p32'), CatalogC.p32)
+        self.assertIs(CatalogC.get('p32'), CatalogC.p32)
 
-        obj = di.Object(object())
+    def test_get_undefined(self):
-        another_obj = di.Object(object())
+        """Test getting of undefined providers using get() method."""
+        self.assertRaises(di.Error, CatalogC.get, 'undefined')
 
-    def test_get_used(self):
+    def test_has(self):
-        """Test retrieving used provider."""
+        """Test checks of providers availability in subsets."""
-        catalog = self.Catalog(self.Catalog.obj)
+        self.assertTrue(CatalogC.has('p11'))
-        self.assertIsInstance(catalog.obj(), object)
+        self.assertTrue(CatalogC.has('p12'))
+        self.assertTrue(CatalogC.has('p21'))
+        self.assertTrue(CatalogC.has('p22'))
+        self.assertTrue(CatalogC.has('p31'))
+        self.assertTrue(CatalogC.has('p32'))
+        self.assertFalse(CatalogC.has('undefined'))
 
-    def test_get_unused(self):
+    def test_is_subset_owner(self):
-        """Test retrieving unused provider."""
+        """Test that catalog is subset owner."""
-        catalog = self.Catalog()
+        subset = CatalogA()
-        self.assertRaises(di.Error, getattr, catalog, 'obj')
 
-    def test_all_providers_by_type(self):
+        self.assertTrue(CatalogA.is_subset_owner(subset))
+        self.assertFalse(CatalogB.is_subset_owner(subset))
+        self.assertFalse(CatalogC.is_subset_owner(subset))
+
+    def test_filter_all_providers_by_type(self):
         """Test getting of all catalog providers of specific type."""
-        self.assertTrue(len(self.Catalog.filter(di.Object)) == 2)
+        self.assertTrue(len(CatalogC.filter(di.Provider)) == 6)
-        self.assertTrue(len(self.Catalog.filter(di.Value)) == 0)
+        self.assertTrue(len(CatalogC.filter(di.Value)) == 0)
 
 
 class OverrideTests(unittest.TestCase):

tests/test_utils.py

@@ -5,7 +5,6 @@ import dependency_injector as di
 
 
 class IsProviderTests(unittest.TestCase):
-
     """`is_provider()` test cases."""
 
     def test_with_instance(self):
@@ -27,7 +26,6 @@ class IsProviderTests(unittest.TestCase):
     def test_with_subclass_instance(self):
         """Test with subclass of provider instance."""
         class SomeProvider(di.Provider):
-
             """Some provider for test."""
 
         self.assertTrue(di.is_provider(SomeProvider()))
@@ -35,7 +33,6 @@ class IsProviderTests(unittest.TestCase):
     def test_with_class_with_getattr(self):
         """Test with class that has __getattr__() method implementation."""
         class SomeClass(object):
-
             """Some test class with __getattr__() method implementation."""
 
             def __getattr__(self, _):
@@ -46,7 +43,6 @@ class IsProviderTests(unittest.TestCase):
 
 
 class EnsureIsProviderTests(unittest.TestCase):
-
     """`ensure_is_provider` test cases."""
 
     def test_with_instance(self):
@@ -68,7 +64,6 @@ class EnsureIsProviderTests(unittest.TestCase):
 
 
 class IsInjectionTests(unittest.TestCase):
-
     """`is_injection()` test cases."""
 
     def test_with_instance(self):
@@ -95,7 +90,6 @@ class IsInjectionTests(unittest.TestCase):
 
 
 class EnsureIsInjectionTests(unittest.TestCase):
-
     """`ensure_is_injection` test cases."""
 
     def test_with_instance(self):
@@ -117,7 +111,6 @@ class EnsureIsInjectionTests(unittest.TestCase):
 
 
 class IsKwArgInjectionTests(unittest.TestCase):
-
     """`is_kwarg_injection()` test cases."""
 
     def test_with_instance(self):
@@ -142,7 +135,6 @@ class IsKwArgInjectionTests(unittest.TestCase):
 
 
 class IsAttributeInjectionTests(unittest.TestCase):
-
     """`is_attribute_injection()` test cases."""
 
     def test_with_instance(self):
@@ -168,7 +160,6 @@ class IsAttributeInjectionTests(unittest.TestCase):
 
 
 class IsMethodInjectionTests(unittest.TestCase):
-
     """`is_method_injection()` test cases."""
 
     def test_with_instance(self):
@@ -193,7 +184,6 @@ class IsMethodInjectionTests(unittest.TestCase):
 
 
 class IsCatalogTests(unittest.TestCase):
-
     """`is_catalog()` test cases."""
 
     def test_with_cls(self):
@@ -207,7 +197,6 @@ class IsCatalogTests(unittest.TestCase):
     def test_with_child_class(self):
         """Test with parent class."""
         class Catalog(di.AbstractCatalog):
-
             """Example catalog child class."""
 
         self.assertTrue(di.is_catalog(Catalog))
@@ -219,3 +208,24 @@ class IsCatalogTests(unittest.TestCase):
     def test_with_object(self):
         """Test with object."""
         self.assertFalse(di.is_catalog(object()))
+
+
+class IsCatalogSubsetTests(unittest.TestCase):
+    """`is_catalog_subset()` test cases."""
+
+    def test_with_cls(self):
+        """Test with class."""
+        self.assertFalse(di.is_catalog_subset(di.CatalogSubset))
+
+    def test_with_instance(self):
+        """Test with class."""
+        self.assertTrue(di.is_catalog_subset(
+            di.CatalogSubset(catalog=di.AbstractCatalog, providers=tuple())))
+
+    def test_with_string(self):
+        """Test with string."""
+        self.assertFalse(di.is_catalog_subset('some_string'))
+
+    def test_with_object(self):
+        """Test with object."""
+        self.assertFalse(di.is_catalog_subset(object()))