Fix broken TestTopology test.

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

@@ -373,18 +373,15 @@ class Residue(object):
 
     def bonds(self):
         """Iterate over all Bonds involving any atom in this residue."""
-        bonds = [ bond for bond in self.chain.topology.bonds() if ((bond[0] in self._atoms) or (bond[1] in self._atoms)) ]
-        return iter(bonds)
+        return ( bond for bond in self.chain.topology.bonds() if ((bond[0] in self._atoms) or (bond[1] in self._atoms)) )
 
     def internal_bonds(self):
         """Iterate over all internal Bonds."""
-        bonds = [ bond for bond in self.chain.topology.bonds() if ((bond[0] in self._atoms) and (bond[1] in self._atoms)) ]
-        return iter(bonds)
+        return ( bond for bond in self.chain.topology.bonds() if ((bond[0] in self._atoms) and (bond[1] in self._atoms)) )
 
     def external_bonds(self):
         """Iterate over all Bonds to external atoms."""
-        bonds = [ bond for bond in self.chain.topology.bonds() if ((bond[0] in self._atoms) != (bond[1] in self._atoms)) ]
-        return iter(bonds)
+        return ( bond for bond in self.chain.topology.bonds() if ((bond[0] in self._atoms) != (bond[1] in self._atoms)) )
 
     def __len__(self):
         return len(self._atoms)

wrappers/python/tests/TestTopology.py

@@ -39,6 +39,9 @@ class TestTopology(unittest.TestCase):
         atom_B1 = topology.addAtom('B1', element.carbon, residue2)
         atom_B2 = topology.addAtom('B2', element.carbon, residue2)
         atom_C1 = topology.addAtom('C1', element.carbon, residue3)
+        topology.addBond(atom_A1, atom_B1)
+        topology.addBond(atom_B1, atom_B2)
+        topology.addBond(atom_B2, atom_C1)
         # Check bonds
         all_bonds = [ bond for bond in residue2.bonds() ]
         internal_bonds = [ bond for bond in residue2.internal_bonds() ]