def test_can_only_add_structures(self):
structure = AtomicStructure(self.atom1, self.atom2)
with self.assertRaises(TypeError):
structure.add("self.chain4")
def test_can_add_structure(self, mock_add):
structure = AtomicStructure(self.atom1, self.atom2)
other = Mock(AtomicStructure)
other._atoms = {self.atom3}
structure.add(other)
mock_add.assert_called_with(self.atom3)