A postcondition is a fact that must always be true just after the execution of some section of code. Postconditions are sometimes tested using assertions within the code itself. Often, postconditions are simply included in the documentation of the affected section of code.
... as also the reindeer in the north, and the musk deer, hares, squirrels, rats and mice everywhere. The avi-fauna is the common Siberian, and the rivers swarm with fish, ...