def test_energy_forces_stress():
    """
    To test that the calculator can produce correct energy and forces.  This
    is done by comparing the energy for an FCC argon lattice with an example
    model to the known value; the forces/stress returned by the model are
    compared to numerical estimates via finite difference.
    """
    import numpy as np
    from pytest import importorskip
    importorskip('kimpy')
    from ase.calculators.kim import KIM
    from ase.lattice.cubic import FaceCenteredCubic

    # Create an FCC atoms crystal
    atoms = FaceCenteredCubic(
        directions=[[1, 0, 0], [0, 1, 0], [0, 0, 1]],
        size=(1, 1, 1),
        symbol="Ar",
        pbc=(1, 0, 0),
        latticeconstant=3.0,
    )

    # Perturb the x coordinate of the first atom by less than the cutoff distance
    atoms.positions[0, 0] += 0.01

    calc = KIM("ex_model_Ar_P_Morse_07C")
    atoms.calc = calc

    # Get energy and analytical forces/stress from KIM model
    energy = atoms.get_potential_energy()
    forces = atoms.get_forces()
    stress = atoms.get_stress()

    # Previously computed energy for this configuration for this model
    energy_ref = 19.7196709065  # eV

    # Compute forces and virial stress numerically
    forces_numer = calc.calculate_numerical_forces(atoms, d=0.0001)
    stress_numer = calc.calculate_numerical_stress(atoms, d=0.0001, voigt=True)

    tol = 1e-6
    assert np.isclose(energy, energy_ref, tol)
    assert np.allclose(forces, forces_numer, tol)
    assert np.allclose(stress, stress_numer, tol)

    # This has been known to segfault
    atoms.set_pbc(True)
    atoms.get_potential_energy()
