def test_bond():
b = Bond(0, 1)
assert b.get_bond_order() == 1
b1 = Bond(1, 0)
assert b == b1
assert b.get_nbr_atom_idx(1) == 0
def test_atom_sharing():
b1 = Bond(0, 1)
b2 = Bond(1, 0)
b3 = Bond(2, 1)
b4 = Bond(3, 2)
assert b1.get_bond_order() == 1
assert b1.shares_atom(b2) == -1 # they are equal
# sharing a single atom
assert b2.shares_atom(b3) == b3.shares_atom(b1)
assert b3.shares_atom(b2) == b2.shares_atom(b3)
# no sharing of atoms
assert b4.shares_atom(b1) == -1
