Add docs and example

docs/containers/check_dependencies.rst

@@ -0,0 +1,18 @@
+.. _check-container-dependencies:
+
+Check container dependencies
+----------------------------
+
+To check container dependencies use method ``.check_dependencies()``.
+
+.. literalinclude:: ../../examples/containers/check_dependencies.py
+   :language: python
+   :lines: 3-
+   :emphasize-lines: 12
+
+Method ``.check_dependencies()`` raises an error if container has any undefined dependencies.
+If all dependencies are provided or have defaults, no error is raised.
+
+See also: :ref:`dependency-provider`.
+
+.. disqus::

docs/containers/index.rst

@@ -24,4 +24,5 @@ Containers module API docs - :py:mod:`dependency_injector.containers`.
     specialization
     overriding
     reset_singletons
+    check_dependencies
     traversal

docs/providers/dependency.rst

@@ -1,3 +1,5 @@
+.. _dependency-provider:
+
 Dependency provider
 ===================
 
@@ -31,4 +33,6 @@ dependency provider will wrap it into the ``Object`` provider.
    :lines: 16-23
    :emphasize-lines: 3
 
+See also: :ref:`check-container-dependencies`.
+
 .. disqus::

examples/containers/check_dependencies.py

@@ -0,0 +1,15 @@
+"""Container dependencies check example."""
+
+from dependency_injector import containers, providers
+
+
+class Container(containers.DeclarativeContainer):
+
+    service1 = providers.Dependency()
+    service2 = providers.Dependency()
+
+
+if __name__ == '__main__':
+    container = Container()
+    container.check_dependencies()  # <-- raises error:
+    # Container has undefined dependencies: "Container.service1", "Container.service2"