def test_charge_methyl_carbocation():
"""Test the charge."""
molecule = Molecule([AtomSpec('C', 3, 1)], [])
assert molecule.charge(0) == 1
def test_charge():
"""Test the charge."""
molecule = Molecule([AtomSpec('C')], [])
assert molecule.charge(0) == 0
def test_charge_given_invalid():
"""Test that invalid atoms raise error when calling charge."""
carb = AtomSpec(6, 4)
molecule = Molecule([carb], [])
with pytest.raises(ValueError):
molecule.charge(1)