Merge pull request #47 from raimis/test

Add a unit test for the Python wrapper

python/tests/TestPlumedForce.py

@@ -0,0 +1,43 @@
+import simtk.openmm as mm
+import simtk.unit as unit
+from openmmplumed import PlumedForce
+import numpy as np
+import unittest
+
+
+class TestTorchForce(unittest.TestCase):
+
+    def testForce(self):
+        # Create a System that applies a force based on the distance between two atoms.
+
+        numParticles = 4
+        system = mm.System()
+        positions = np.empty((numParticles, 3))
+        for i in range(numParticles):
+            system.addParticle(1.0)
+            positions[i] = [i, 0.1*i, -0.3*i]
+        script = '''
+            d: DISTANCE ATOMS=1,3
+            BIASVALUE ARG=d
+        '''
+        force = PlumedForce(script)
+        system.addForce(force)
+        integ = mm.LangevinIntegrator(300.0, 1.0, 1.0)
+        context = mm.Context(system, integ, mm.Platform.getPlatformByName('Reference'))
+        context.setPositions(positions)
+
+        # Compute the forces and energy.
+
+        state = context.getState(getEnergy=True, getForces=True)
+        delta = positions[0] - positions[2] 
+        dist = np.sqrt(np.sum(delta**2))
+        zero = np.zeros(3)
+        self.assertAlmostEqual(dist, state.getPotentialEnergy().value_in_unit(unit.kilojoules_per_mole))
+        self.assertTrue(np.allclose(-delta/dist, state.getForces(asNumpy=True)[0]))
+        self.assertTrue(np.allclose(zero, state.getForces(asNumpy=True)[1]))
+        self.assertTrue(np.allclose(delta/dist, state.getForces(asNumpy=True)[2]))
+        self.assertTrue(np.allclose(zero, state.getForces(asNumpy=True)[3]))
+
+
+if __name__ == '__main__':
+    unittest.main()