Make Step.behave_as fail when calling an undefined step

lettuce/core.py

@@ -356,15 +356,15 @@ class Step(object):
             for step in steps:
                 step.scenario = self.scenario
 
-        (_, _, steps_failed, _, _) = self.run_all(steps)
-        if not steps_failed:
+        (_, _, steps_failed, steps_undefined, _) = self.run_all(steps)
+        if not steps_failed and not steps_undefined:
             self.passed = True
             self.failed = False
             return self.passed
-        else:
-            self.passed = False
-            self.failed = True
-            assert not steps_failed, steps_failed[0].why.exception
+        self.passed = False
+        self.failed = True
+        assert not steps_failed, steps_failed[0].why.exception
+        assert not steps_undefined, "Undefined step: %s" % steps_undefined[0].sentence
 
     def run(self, ignore_case):
         """Runs a step, trying to resolve it on available step

tests/unit/test_step_runner.py

@@ -437,6 +437,30 @@ def test_failing_behave_as_step_fails():
     assert runnable_step.failed
 
 @with_setup(step_runner_environ)
+def test_undefined_behave_as_step_doesnt_pass():
+    'When a step definition calls an undefined step definition with behave_as, that step should not be marked as success.'
+    runnable_step = Step.from_string('Given I have a step which calls the "undefined step" step with behave_as')
+    try:
+        runnable_step.run(True)
+        assert False, "Undefined step should raise exception"
+    except:
+        pass
+
+    assert_false(runnable_step.passed)
+
+@with_setup(step_runner_environ)
+def test_undefined_behave_as_step_fails():
+    'When a step definition calls an undefined step definition with behave_as, that step should be marked a failure.'
+    runnable_step = Step.from_string('Given I have a step which calls the "undefined step" step with behave_as')
+    try:
+        runnable_step.run(True)
+        assert False, "Undefined step should raise exception"
+    except Exception, e:
+        pass
+
+    assert runnable_step.failed
+
+@with_setup(step_runner_environ)
 def test_failing_behave_as_step_raises_assertion():
     'When a step definition calls another (failing) step definition with behave_as, that step should be marked a failure.'
     runnable_step = Step.from_string('Given I have a step which calls the "other step fails" step with behave_as')