Fix state.generate_testcase (#451)

* Use correct event name

* Add test for state.generate_testcase

Test merely tests that this function publishes the 'will_generate_testcase' event

* Properly test; make sure the callback executes and error if not

This is the most convoluted unit test I've ever written.

* "better"

manticore/core/state.py

@@ -372,4 +372,4 @@ class State(Eventful):
         :param str name: Short string identifying this testcase used to prefix workspace entries.
         :param str message: Longer description
         """
-        self.publish('will_generate_inputs', name, message)
+        self.publish('will_generate_testcase', name, message)

tests/test_state.py

@@ -4,6 +4,10 @@ from manticore.platforms import linux
 from manticore.core.state import State
 from manticore.core.smtlib import BitVecVariable, ConstraintSet
 
+class _CallbackExecuted(Exception):
+    pass
+
+
 class FakeMemory(object):
     def __init__(self):
         self._constraints = None
@@ -196,4 +200,14 @@ class StateTest(unittest.TestCase):
         self.assertEqual( new_state.context['step'], 20)
         new_new_state = pickle.loads(new_new_file)
         self.assertEqual( new_new_state.context['step'], 30)
-        
+
+
+    def _test_state_gen_helper(self, name, msg):
+        self.assertEqual(name, 'statename')
+        self.assertEqual(msg, 'statemsg')
+        raise _CallbackExecuted
+
+    def test_state_gen(self):
+        self.state.subscribe('will_generate_testcase', self._test_state_gen_helper)
+        with self.assertRaises(_CallbackExecuted):
+            self.state.generate_testcase('statename', 'statemsg')