test energy and forces produced by MLFFs in test_ext_load

tests/forcefields/test_utils.py

@@ -1,3 +1,4 @@
+import numpy as np
 import pytest
 
 from atomate2.forcefields import MLFF
@@ -11,6 +12,8 @@ def test_mlff(mlff: MLFF):
 
 @pytest.mark.parametrize("mlff", ["CHGNet", "MACE", MLFF.MatterSim, MLFF.SevenNet])
 def test_ext_load(mlff: str):
+    from ase.build import bulk
+
     decode_dict = {
         "CHGNet": {"@module": "chgnet.model.dynamics", "@callable": "CHGNetCalculator"},
         "MACE": {"@module": "mace.calculators", "@callable": "mace_mp"},
@@ -29,6 +32,17 @@ def test_ext_load(mlff: str):
     assert calc_from_decode.name == calc_from_preset.name
     assert calc_from_decode.parameters == calc_from_preset.parameters == {}
 
+    atoms = bulk("Si", "diamond", a=5.43)
+
+    atoms.calc = calc_from_preset
+    energy = atoms.get_potential_energy()
+    forces = atoms.get_forces()
+
+    assert isinstance(energy, float | np.floating)
+    assert energy < 0
+    assert forces.shape == (2, 3)
+    assert abs(forces.sum()) < 1e-6, f"unexpectedly large net {forces=}"
+
 
 def test_raises_error():
     with pytest.raises(ValueError, match="Could not create"):