runForClockTime() updates currentStep correctly

wrappers/python/simtk/openmm/app/simulation.py

@@ -196,10 +196,11 @@ class Simulation(object):
             while stepsToGo > 10:
                 self.integrator.step(10) # Only take 10 steps at a time, to give Python more chances to respond to a control-c.
                 stepsToGo -= 10
+                self.currentStep += 10
                 if endTime is not None and datetime.now() >= endTime:
                     return
             self.integrator.step(stepsToGo)
-            self.currentStep += nextSteps
+            self.currentStep += stepsToGo
             if anyReport:
                 # One or more reporters are ready to generate reports.  Organize them into three
                 # groups: ones that want wrapped positions, ones that want unwrapped positions,

wrappers/python/tests/TestSimulation.py

@@ -147,6 +147,12 @@ class TestSimulation(unittest.TestCase):
         self.assertTrue(endTime >= startTime+timedelta(seconds=5))
         self.assertTrue(endTime < startTime+timedelta(seconds=10))
         
+        # Check that the time and step count are consistent.
+        
+        time = simulation.context.getState().getTime().value_in_unit(picoseconds)
+        expectedTime = simulation.currentStep*integrator.getStepSize().value_in_unit(picoseconds)
+        self.assertAlmostEqual(expectedTime, time)
+
         # Load the checkpoint and state and make sure they are both correct.
 
         velocities = simulation.context.getState(getVelocities=True).getVelocities()