diff --git a/bonobo/execution/contexts/base.py b/bonobo/execution/contexts/base.py
index 4647d91..b7f07c5 100644
--- a/bonobo/execution/contexts/base.py
+++ b/bonobo/execution/contexts/base.py
@@ -99,9 +99,6 @@ class Lifecycle:
 
         self._stopped = True
 
-        if self._stopped:  # Stopping twice has no effect
-            return
-
     def kill(self):
         if not self.started:
             raise RuntimeError('Cannot kill an unstarted context.')
@@ -136,3 +133,12 @@ class BaseContext(Lifecycle, Wrapper):
         Lifecycle.__init__(self)
         Wrapper.__init__(self, wrapped)
         self.parent = parent
+
+    @property
+    def xstatus(self):
+        """
+        UNIX-like exit status, only coherent if the context has stopped.
+        """
+        if self._defunct:
+            return 70
+        return 0
diff --git a/bonobo/execution/contexts/graph.py b/bonobo/execution/contexts/graph.py
index a6559a3..3c029b5 100644
--- a/bonobo/execution/contexts/graph.py
+++ b/bonobo/execution/contexts/graph.py
@@ -4,12 +4,17 @@ from time import sleep
 from bonobo.config import create_container
 from bonobo.constants import BEGIN, END
 from bonobo.execution import events
+from bonobo.execution.contexts.base import BaseContext
 from bonobo.execution.contexts.node import NodeExecutionContext
 from bonobo.execution.contexts.plugin import PluginExecutionContext
 from whistle import EventDispatcher
 
 
-class GraphExecutionContext:
+class GraphExecutionContext(BaseContext):
+    """
+    Stores the actual state of a graph execution, and manages its lifecycle.
+
+    """
     NodeExecutionContextType = NodeExecutionContext
     PluginExecutionContextType = PluginExecutionContext
 
@@ -17,17 +22,24 @@ class GraphExecutionContext:
 
     @property
     def started(self):
+        if not len(self.nodes):
+            return super(GraphExecutionContext, self).started
         return any(node.started for node in self.nodes)
 
     @property
     def stopped(self):
+        if not len(self.nodes):
+            return super(GraphExecutionContext, self).stopped
         return all(node.started and node.stopped for node in self.nodes)
 
     @property
     def alive(self):
+        if not len(self.nodes):
+            return super(GraphExecutionContext, self).alive
         return any(node.alive for node in self.nodes)
 
-    def __init__(self, graph, plugins=None, services=None, dispatcher=None):
+    def __init__(self, graph, *, plugins=None, services=None, dispatcher=None):
+        super(GraphExecutionContext, self).__init__(graph)
         self.dispatcher = dispatcher or EventDispatcher()
         self.graph = graph
         self.nodes = [self.create_node_execution_context_for(node) for node in self.graph]
@@ -74,6 +86,8 @@ class GraphExecutionContext:
         self.dispatcher.dispatch(name, events.ExecutionEvent(self))
 
     def start(self, starter=None):
+        super(GraphExecutionContext, self).start()
+
         self.register_plugins()
         self.dispatch(events.START)
         self.tick(pause=False)
@@ -89,13 +103,16 @@ class GraphExecutionContext:
         if pause:
             sleep(self.TICK_PERIOD)
 
-    def kill(self):
-        self.dispatch(events.KILL)
-        for node_context in self.nodes:
-            node_context.kill()
-        self.tick()
+    def loop(self):
+        while self.should_loop:
+            self.tick()
+            for node in self.nodes:
+                if node.should_loop:
+                    node.step()
 
     def stop(self, stopper=None):
+        super(GraphExecutionContext, self).stop()
+
         self.dispatch(events.STOP)
         for node_context in self.nodes:
             if stopper is None:
@@ -106,6 +123,14 @@ class GraphExecutionContext:
         self.dispatch(events.STOPPED)
         self.unregister_plugins()
 
+    def kill(self):
+        super(GraphExecutionContext, self).kill()
+
+        self.dispatch(events.KILL)
+        for node_context in self.nodes:
+            node_context.kill()
+        self.tick()
+
     def register_plugins(self):
         for plugin_context in self.plugins:
             plugin_context.register()
diff --git a/bonobo/execution/contexts/node.py b/bonobo/execution/contexts/node.py
index cf9ec67..07cbf16 100644
--- a/bonobo/execution/contexts/node.py
+++ b/bonobo/execution/contexts/node.py
@@ -21,6 +21,15 @@ UnboundArguments = namedtuple('UnboundArguments', ['args', 'kwargs'])
 
 
 class NodeExecutionContext(BaseContext, WithStatistics):
+    """
+    Stores the actual context of a node, within a given graph execution, accessed as `self.parent`.
+
+    A special case exist, mostly for testing purpose, where there is no parent context.
+
+    Can be used as a context manager, also very convenient for testing nodes that requires some external context (like
+    a service implementation, or a value holder).
+
+    """
     def __init__(self, wrapped, *, parent=None, services=None, _input=None, _outputs=None):
         """
         Node execution context has the responsibility fo storing the state of a transformation during its execution.
@@ -170,7 +179,7 @@ class NodeExecutionContext(BaseContext, WithStatistics):
         if self._stack:
             try:
                 self._stack.teardown()
-            except:
+            except Exception as exc:
                 self.fatal(sys.exc_info())
 
         super().stop()
diff --git a/tests/execution/contexts/test_execution_contexts_graph.py b/tests/execution/contexts/test_execution_contexts_graph.py
new file mode 100644
index 0000000..95b1ea4
--- /dev/null
+++ b/tests/execution/contexts/test_execution_contexts_graph.py
@@ -0,0 +1,59 @@
+from bonobo import Graph
+from bonobo.execution.contexts import GraphExecutionContext
+
+
+def raise_an_error(*args, **kwargs):
+    raise Exception('Careful, man, there\'s a beverage here!')
+
+
+def raise_an_unrecoverrable_error(*args, **kwargs):
+    raise Exception('You are entering a world of pain!')
+
+
+def test_lifecycle_of_empty_graph():
+    graph = Graph()
+    with GraphExecutionContext(graph) as context:
+        assert context.started
+        assert context.alive
+        assert not context.stopped
+    assert context.started
+    assert not context.alive
+    assert context.stopped
+    assert not context.xstatus
+
+
+def test_lifecycle_of_nonempty_graph():
+    graph = Graph([1, 2, 3], print)
+    with GraphExecutionContext(graph) as context:
+        assert context.started
+        assert context.alive
+        assert not context.stopped
+    assert context.started
+    assert not context.alive
+    assert context.stopped
+    assert not context.xstatus
+
+
+def test_lifecycle_of_graph_with_recoverable_error():
+    graph = Graph([1, 2, 3], raise_an_error, print)
+    with GraphExecutionContext(graph) as context:
+        assert context.started
+        assert context.alive
+        assert not context.stopped
+    assert context.started
+    assert not context.alive
+    assert context.stopped
+    assert not context.xstatus
+
+
+def test_lifecycle_of_graph_with_unrecoverable_error():
+    graph = Graph([1, 2, 3], raise_an_unrecoverrable_error, print)
+    with GraphExecutionContext(graph) as context:
+        assert context.started
+        assert context.alive
+        assert not context.stopped
+        context.loop()
+    assert context.started
+    assert not context.alive
+    assert context.stopped
+    assert not context.xstatus