add test

wrappers/python/tests/TestCheckpointReporter.py

+import unittest
+import tempfile
+from simtk.openmm import app
+import simtk.openmm as mm
+from simtk import unit
+
+
+class TestCheckpointReporter(unittest.TestCase):
+    def setUp(self):
+        pdb = app.PDBFile('systems/alanine-dipeptide-implicit.pdb')
+        forcefield = app.ForceField('amber99sbildn.xml')
+        system = forcefield.createSystem(pdb.topology, 
+            nonbondedMethod=app.CutoffNonPeriodic, nonbondedCutoff=1.0*unit.nanometers, 
+            constraints=app.HBonds)
+        self.simulation = app.Simulation(pdb.topology, system, mm.VerletIntegrator(0.002*unit.picoseconds))
+        self.simulation.context.setPositions(pdb.positions)
+        
+    def test_1(self):
+        file = tempfile.NamedTemporaryFile()
+        self.simulation.reporters.append(app.CheckpointReporter(file, 1))
+        self.simulation.step(1)
+        
+
+
+if __name__ == '__main__':
+    unittest.main()
\ No newline at end of file