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import pytest
import numpy as np
from ase.constraints import Hookean, FixAtoms
from ase.build import molecule
@pytest.fixture
def atoms():
return molecule('CH3CH2OH')
def test_momenta_fixatoms(atoms):
atoms.set_constraint(FixAtoms(indices=[0]))
atoms.set_momenta(np.ones(atoms.get_momenta().shape))
desired = np.ones(atoms.get_momenta().shape)
desired[0] = 0.
actual = atoms.get_momenta()
assert (actual == desired).all()
def test_momenta_hookean(atoms):
atoms.set_constraint(Hookean(0, 1, rt=1., k=10.))
atoms.set_momenta(np.zeros(atoms.get_momenta().shape))
actual = atoms.get_momenta()
desired = np.zeros(atoms.get_momenta().shape)
# Why zero memoenta? Should we not test something juicier?
assert (actual == desired).all()
def test_get_set_velocities(atoms):
shape = (len(atoms), 3)
assert np.array_equal(atoms.get_velocities(), np.zeros(shape))
rng = np.random.RandomState(17)
v0 = rng.rand(*shape)
atoms.set_velocities(v0)
assert atoms.get_velocities() == pytest.approx(v0)
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