Currently, if a Chryssalid makes an attack against one of your soldiers, it deals damage based on the Chryssalid's strength. If the soldier is killed, a zombie spawns in its place. The Chryssalid may then cease the attack and go for a different soldier. But if the Chryssalid runs out of time units and still has not depleted the soldier's hit points, it will stop attacking and the soldier is killed anyway.
This can be tested with a soldier that has 250 armor, as the Chryssalid will be unable to cause any damage to the soldier. If you set the Chryssalid's attack to 1 TU cost, it will make a very large number of attacks, completely draining its remaining TUs to attack because it consistently fails. However at the end of its turn, the soldier is turned into a zombie anyway.
How do I turn off this function, so that the Chryssalid is required to actually kill the soldier in order to turn them into a zombie?