Add implementation + tests

src/dependency_injector/containers.pyi

@@ -43,6 +43,8 @@ class Container:
     def unwire(self) -> None: ...
     def init_resources(self) -> Optional[Awaitable]: ...
     def shutdown_resources(self) -> Optional[Awaitable]: ...
+    def apply_container_providers_overridings(self) -> None: ...
+    def reset_singletons(self) -> None: ...
     @overload
     def traverse(self, types: Optional[Sequence[Type]] = None) -> Iterator[Provider]: ...
     @classmethod

src/dependency_injector/containers.pyx

@@ -271,6 +271,11 @@ class DynamicContainer(Container):
         for provider in self.traverse(types=[providers.Container]):
             provider.apply_overridings()
 
+    def reset_singletons(self):
+        """Reset all container singletons."""
+        for provider in self.traverse(types=[providers.Singleton]):
+            provider.reset()
+
 
 class DeclarativeContainerMetaClass(type):
     """Declarative inversion of control container meta class."""

tests/unit/containers/test_dynamic_py2_py3.py

@@ -287,3 +287,51 @@ class DeclarativeContainerInstanceTests(unittest.TestCase):
         self.assertEqual(_init1.shutdown_counter, 2)
         self.assertEqual(_init2.init_counter, 2)
         self.assertEqual(_init2.shutdown_counter, 2)
+
+    def reset_singletons(self):
+        class SubSubContainer(containers.DeclarativeContainer):
+            singleton = providers.Singleton(object)
+
+        class SubContainer(containers.DeclarativeContainer):
+            singleton = providers.Singleton(object)
+            sub_sub_container = providers.Container(SubSubContainer)
+
+        class Container(containers.DeclarativeContainer):
+            singleton = providers.Singleton(object)
+            sub_container = providers.Container(SubContainer)
+
+        container = Container()
+
+        obj11 = container.singleton()
+        obj12 = container.sub_container().singleton()
+        obj13 = container.sub_container().sub_sub_container().singleton()
+
+        obj21 = container.singleton()
+        obj22 = container.sub_container().singleton()
+        obj23 = container.sub_container().sub_sub_container().singleton()
+
+        self.assertIs(obj11, obj21)
+        self.assertIs(obj12, obj22)
+        self.assertIs(obj13, obj23)
+
+        container.reset_singletons()
+
+        obj31 = container.singleton()
+        obj32 = container.sub_container().singleton()
+        obj33 = container.sub_container().sub_sub_container().singleton()
+
+        obj41 = container.singleton()
+        obj42 = container.sub_container().singleton()
+        obj43 = container.sub_container().sub_sub_container().singleton()
+
+        self.assertIsNot(obj11, obj31)
+        self.assertIsNot(obj12, obj32)
+        self.assertIsNot(obj13, obj33)
+
+        self.assertIsNot(obj21, obj31)
+        self.assertIsNot(obj22, obj32)
+        self.assertIsNot(obj23, obj33)
+
+        self.assertIs(obj31, obj41)
+        self.assertIs(obj32, obj42)
+        self.assertIs(obj33, obj43)