Add a simple unit test for get_energy

tests/test_get_energy.py

@@ -0,0 +1,23 @@
+import ase.build
+from ase.calculators.singlepoint import SinglePointCalculator
+import ase.io
+import pytest
+
+from mctools.generic.get_energy import get_energy
+
+
+ENERGY = 3.141
+FILENAME = "methane.extxyz"
+
+
+@pytest.fixture
+def methane_with_energy() -> ase.Atoms:
+    atoms = ase.build.molecule("CH4")
+    atoms.calc = SinglePointCalculator(atoms, energy=ENERGY)
+    return atoms
+
+
+def test_get_energy(methane_with_energy, tmp_path) -> None:
+    ase.io.write(tmp_path / FILENAME, methane_with_energy)
+
+    assert get_energy(tmp_path / FILENAME) == pytest.approx(ENERGY)